Decoding Bottle Numbers: How to Identify Old Bottles by Numbers on the Bottom
Learn how to identify old bottles by numbers on the bottom. Our comprehensive guide explains bottle base codes, manufacturer marks, and what those mysterious mold numbers really mean.
By Appraisily TeamLast updated July 20, 2023
Discovering an old bottle with mysterious numbers on the bottom can feel like finding a secret code. These embossed digits and symbols are more than just manufacturing quirks—they’re valuable clues that can help you identify a bottle’s age, origin, and potential value. Whether you’re a seasoned collector or just curious about an old bottle you’ve found, understanding how to “read” these bottom marks is essential for proper identification.
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<span>Understanding Numbers on Bottle Bottoms</span>
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<div class="section-header__body">The numbers and markings on the bottom of glass bottles serve various purposes in the manufacturing process. Knowing what these codes mean can help you accurately date and identify your bottle.</div>
When examining the bottom of an old bottle, you’ll often find a variety of markings. These can include numbers, letters, symbols, or combinations of all three. While some markings clearly identify the manufacturer, others indicate more technical aspects of the bottle’s production.
In most cases, one- or two-digit numbers found on bottle bottoms are mold numbers. These numbers served to identify the specific bottle mold or section in an automatic bottle machine. If multiple identical molds were used in production, each one received its own identifying number.
Other numerical markings might indicate:
Bottle style or catalog number
Year of manufacture
Plant location codes
Glass formula identification
Understanding these codes requires some knowledge of glass manufacturing history and techniques. Let’s explore the most common types of bottle bottom markings and what they reveal.
Bottle Base Marking Facts
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<span>Types of Bottle Bottom Numbers</span>
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<div class="section-header__body">Not all numbers on bottle bottoms serve the same purpose. Learning to distinguish between different types of numerical markings is key to proper bottle identification.</div>
Mold Numbers
The most common numbers found on bottle bottoms are mold numbers, typically appearing as single or double digits. These numbers were used by glass manufacturers to identify specific molds or sections of automatic bottle machines.
Glass factories often operated multiple molds simultaneously to increase production efficiency. By numbering each mold, manufacturers could:
Track production output from each mold
Identify quality control issues specific to a particular mold
Document when molds needed maintenance or replacement
Mold numbers don’t typically provide information about the bottle’s age or origin—they were purely for internal factory use.
Date Codes
Some bottles feature numbers that indicate manufacturing dates. Date codes can appear in several formats:
Single or double-digit year: A single number like “7” might indicate manufacture in 1937, 1947, etc. Context clues like bottle style help narrow down the decade.
Two-digit year: Numbers like “42” commonly represent 1942.
Date-month combination: Numbers like “15-6” might indicate June 1915.
Date codes became more standardized in the 20th century, particularly after the 1940s, when many glass companies adopted clearer dating systems.
Plant Codes
Many glass manufacturers operated multiple factories. Numbers on bottle bottoms sometimes indicated which plant produced the bottle. These codes were often used alongside manufacturer’s marks.
For instance, the Owens-Illinois Glass Company used a numerical plant code system, where the number to the left of their trademark indicated the manufacturing plant, and the number to the right typically indicated the year of manufacture.
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<span>Manufacturer's Marks and Codes</span>
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<div class="section-header__body">Beyond simple numbers, many bottles feature distinctive makers’ marks that can help identify their origin and approximate age.</div>
Manufacturer’s marks are perhaps the most useful markings for bottle identification. These are embossed symbols, letters, or logos that identify which glass company produced the bottle. When used in combination with numerical codes, they provide valuable dating information.
Some common manufacturer’s marks include:
Owens-Illinois: An “I” inside an “O” or diamond, used from 1929 onwards
Hazel-Atlas: An “H” over an “A”, used from 1923 to 1964
Ball: The word “BALL” in script or block letters
Brockway Glass: A “B” inside a circle or the letters “BGCO”
Anchor Hocking: An anchor symbol or “AH” mark
The Society for Historical Archaeology (SHA) maintains an extensive database of bottle makers’ marks that can help you identify these symbols.
Value Ranges for Common Antique Bottles
Market values based on condition and rarity
Category
Price
Notes
Pre-1900 Embossed Medicine Bottles
$20-$200+
Higher values for rare medicines or ornate embossing
Milk Bottles with Local Dairy Names
$10-$75
Value increases with age and local significance
Coca-Cola Bottles (Pre-1950)
$5-$150
Rare city names or unusual marks increase value
Colored Glass Bottles (Pre-1920)
$25-$300+
Unusual colors command highest prices
Whiskey/Liquor Bottles (Pre-1900)
$50-$500+
Value based on brand, condition, and embossing
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<span>Dot Codes and Stippling Patterns</span>
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<div class="section-header__body">The arrangement of dots on a bottle bottom may look random, but they often form a specific code that provides manufacturing information.</div>
Modern bottles often feature dot patterns or stippling on their bases. While these dots serve practical manufacturing purposes (helping release the bottle from the mold), they can also contain encoded information.
Dot patterns might indicate:
The specific mold cavity that made the bottle
The date of manufacture (in a dot-code format)
Quality control tracking information
For example, a pattern showing “four dots, space, one dot, space, four dots” could represent a specific mold position in the manufacturing line or a particular production date.
These dot codes became more common after the 1940s with the widespread adoption of automated bottle-making machines. The specific meaning of dot patterns often varied between glass manufacturers, making them challenging to decode without company-specific references.
Evolution of Bottle Base Markings
1800-1880
Early Hand-Blown Era
Bottles were predominantly handmade with few consistent markings. Pontil scars (rough circular marks) on bottle bases indicate hand-blown production.
1880-1910
Semi-Automatic Production
Introduction of semi-automatic bottle machines. Manufacturer marks began appearing with more consistency. Single-digit mold numbers became common.
1910-1930
Early Automatic Era
Widespread adoption of Owens Automatic Bottle Machine. Standardized manufacturer marks, plus mold numbers and basic date codes.
1930-1950
Standardized Coding Systems
Major manufacturers developed consistent date and plant coding systems. Two and three-digit date codes became standard.
1950-Present
Modern Coding Systems
Introduction of more complex dot codes, stippling patterns, and manufacturer symbols. Addition of recycling codes on plastic bottles.
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<span>Using Mold Seams and Production Techniques for Dating</span>
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<div class="section-header__body">While not directly related to base numbers, understanding how bottle production techniques evolved can provide important context for interpreting numerical codes.</div>
Bottle production technology changed significantly over time, and these changes left visible marks on the bottles. When combined with base numbers, these manufacturing clues can help narrow down a bottle’s age:
Pontil Marks (pre-1860s): A rough circular scar on the bottle base indicates it was handmade using a pontil rod. These bottles rarely have mold numbers.
Mold Seams (1860s-1920): Visible seam lines on the bottle’s body indicate it was made in a mold. The height of these seams helps date the bottle:
Seams ending at the neck: 1860s-1880s
Seams extending onto the neck: 1880s-1910s
Seams all the way to the lip: After 1910
Suction Scars (1905-1920s): Distinctive circular or oval marks on the bottle bottom from Owens Automatic Bottle Machines.
Valve Marks (1930s-present): Small, off-center circular marks on the bottom from modern automated production.
Take clear photos or make detailed sketches of all markings.
Step 2: Identify Manufacturer’s Marks
Before focusing on numbers, try to identify any manufacturer’s marks or logos. These provide critical context for interpreting the numbers. Use reference resources like:
Once you’ve identified the manufacturer (if possible), examine the numbers:
Single digits (1-9) are typically mold numbers
Two-digit numbers might be mold numbers, plant codes, or year codes
Three or more digits often indicate catalog numbers or date codes
For Owens-Illinois bottles, for example, the number to the left of the logo is the plant number, and the number to the right is typically the year of manufacture.
Step 4: Consider Bottle Style and Use
The bottle’s shape, color, and intended purpose provide important context:
Medicine bottles often have different coding systems than beverage bottles
Food bottles might use different numbering than cosmetic bottles
Milk bottles frequently used date codes related to dairy regulations
Step 5: Cross-Reference with Multiple Sources
Bottle identification is sometimes more art than science. Cross-reference your findings with multiple sources and consider joining bottle collecting forums where experts can help interpret unusual markings.
<span>Common Bottle Manufacturer Marks and Their History</span>
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<div class="section-header__body">Recognizing these common bottle manufacturer marks will help you narrow down when and where your bottle was made.</div>
Owens-Illinois Glass Company (1929-present)
Mark: “I” inside an “O” or diamond
Numbering System: Plant number (left) and year (right)
Plant numbers range from 1-32, representing different factory locations
Year numbers are single or double digits (e.g., “4” for 1934 or 1944, context determines decade)
Hazel-Atlas Glass Company (1902-1964)
Mark: “H” over an “A”
Numbering System: Often includes a single-digit mold number
After 1923, may include a date code (single digit for year)
Ball Brothers Glass Manufacturing Company (1880s-present)
Mark: “BALL” in script or block letters
Numbering System: Simple mold numbers or sometimes year codes
Style of the Ball logo itself helps date the bottle
Anchor Hocking Glass Corporation (1937-present)
Mark: Anchor symbol, sometimes with “H” or numbers
Numbering System: Plant and date codes vary by era
Brockway Glass Company (1907-1988)
Mark: “B” in a circle or “BGCO”
Numbering System: Mold numbers and later date codes after the 1950s
These major manufacturers had fairly consistent marking systems, but many smaller glass companies used less standardized approaches. Regional bottle makers might use their own unique marking systems or simply their initials.
Common Questions About Bottle Bottom Numbers
What do one- or two-digit numbers on the bottom of glass bottles mean?
In most cases, one- or two-digit numbers on bottle bottoms are mold numbers. These numbers identified the specific bottle mold or section in an automatic bottle machine. If multiple identical molds were used in production, each received its own number. These numbers were primarily for quality control and manufacturing purposes, allowing factories to track which molds produced which bottles.
How can I tell how old a bottle is from the bottom markings?
Dating a bottle based on bottom markings requires analyzing several factors:
Identify any manufacturer’s marks and research when that company was in operation
Look for date codes (some manufacturers included year numbers)
Examine production techniques (pontil marks, mold seams, etc.)
Consider the bottle’s physical characteristics (color, shape, seams)
The most reliable dating comes from combining information from base markings with physical characteristics. For example, if a bottle has an Owens-Illinois mark with numbers "7" and "41", and the seams extend all the way to the lip, you can confidently date it to 1941, manufactured at plant #7.
What are the dots or stippling patterns on modern bottle bottoms?
Dot patterns or stippling on bottle bottoms serve multiple purposes:
Manufacturing function: The raised dots help release the bottle from the mold and allow even distribution of glass during formation
Mold identification: Specific patterns can identify which mold cavity produced the bottle
Date/batch coding: Some manufacturers use dot patterns as a form of code to indicate production date or batch
Quality control: Dot patterns can help trace production issues back to specific manufacturing equipment
The specific meaning of dot patterns varies between manufacturers, making them challenging to decode without company-specific references.
Are there apps that can help identify old bottles by their bottom markings?
While there isn't yet a comprehensive "Shazam for bottles" that can instantly identify any bottle from its base markings, several apps and online resources can help:
General antique identification apps: Applications like Google Lens can sometimes identify common bottle types or direct you to similar images online
Collector community platforms: Apps and websites where you can upload images for identification by knowledgeable collectors
Reference databases: Online databases of bottle makers’ marks and numerical codes
The most reliable bottle identification still comes from combining technology with research and expert knowledge. Collector forums and communities remain invaluable resources for identifying unusual or rare bottles.
How do I read Owens-Illinois bottle codes?
Owens-Illinois bottle codes follow a relatively standardized format, especially after 1940:
"⬦" = Owens-Illinois maker’s mark (diamond with "I" inside)
"46" = Year 1946
Some bottles might include additional numbers that indicate mold cavities or other production information. Between 1929-1954, Owens-Illinois used single-digit year codes, requiring context to determine the decade (e.g., "9" could be 1939 or 1949). After 1954, they typically used two-digit year codes.
Can the numbers on bottle bottoms determine their value?
While numbers alone rarely determine a bottle's value, they can contribute significantly by helping:
Confirm authenticity: Correct manufacturer marks and date codes can verify a bottle is genuinely from the period claimed
Establish rarity: Some manufacturing plants or production years were more limited than others
Identify special productions: Certain mold numbers or codes might indicate limited editions or special production runs
Bottle value is primarily determined by rarity, condition, aesthetic appeal, historical significance, and collector demand. The numbers and marks help establish provenance, which affects these value factors. For example, a rare color bottle with confirmed early dating from bottom marks would be worth more than a similar bottle without verifiable age.
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<span>Conclusion: The Value of Understanding Bottle Bottom Numbers</span>
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<div class="section-header__body">Decoding the numbers and markings on bottle bottoms connects us to the rich history of glass manufacturing and provides crucial clues for bottle identification.</div>
The seemingly cryptic numbers and symbols on bottle bottoms are windows into manufacturing history, offering important clues about when, where, and how a bottle was made. While these markings were originally intended for factory quality control and production tracking, they now serve as valuable tools for collectors, archaeologists, and anyone interested in historical artifacts.
Learning to read these codes not only helps with accurate bottle identification but also enhances appreciation for the technological evolution of glass manufacturing. From handblown bottles with pontil scars to machine-made containers with precise dot codes, each marking tells part of the story of industrial development.
For collectors, proper identification through bottom markings can significantly impact a bottle’s value and historical significance. For casual finders, these marks transform an ordinary old bottle into a tangible connection to the past.
The next time you find an old bottle, take a moment to examine its base. Those numbers and symbols are more than random markings—they’re pieces of a historical puzzle waiting to be solved.
