The Ultimate Guide To Identifying Marks On Old Bottles Tips And Tricks For Collectors

For bottle collectors and appraisers, marks are the fastest, most reliable way to place a piece in time, tie it to a glasshouse, and separate a common container from a meaningful artifact. This guide walks you through where to look, what to look for, and how to read the clues accurately—without overreaching.

Where To Look: The Anatomy Of Bottle Marks

Before decoding, know the common mark locations and terms:

• Base: The bottom is the richest area for maker’s marks, date codes, mold numbers, suction scars, and pontil scars.
• Heel: The rim between base and sidewall sometimes carries capacity, deposit, or property statements, or a glasshouse logo.
• Body/Panel: Brand names, city/state, pharmacy proprietors, and pictorial trademarks are commonly embossed here. Applied color labels (painted/pyroglaze) appear from the 1930s onward.
• Shoulder: Occasionally used for capacity (e.g., “FULL PINT”) or proprietary embossing on bitters, medicines, and sodas.
• Neck and Finish (Lip): Finish type (blob, crown, lightning, screw-thread) helps date and identify function. Mold seams at the lip are key to manufacturing method.

Embossing can be raised (embossed) or incised (debossed). Base stippling (a pebbled texture) is frequent on mid-20th-century machine-made bottles to prevent scuffing.

Base Clues: Pontils, Suction Rings, Logos, And Date Codes

The base tells a tight story when you know how to read it.

Pontil scars (hand-blown era):

• Open pontil: Rough, glassy, often sharp scar from a rod detached at the base; most common on early to mid-19th-century bottles and flasks.
• Sand or disk pontil: Ground-looking, sometimes with sand inclusions; also 19th century.
• Iron/rod or blowpipe pontil: Narrower, smoother scar than open pontil; later 19th century. Note: A genuine pontil scar is integral to the glass, not glued or acid-etched. Modern fakes may have an “added” rough spot that doesn’t feather into the base glass.

Machine-era base features:

• Owens suction scar: Often a circular or crescent, slightly off-center mark created by the Owens Automatic Bottle Machine (early 1900s through the 1930s in many plants). The scar may have faint concentric striations.
• Cup-bottom mold: A neat circular base seam with no pontil. Dominant from late 19th century onward (hand and machine).
• Stippling and code clusters: Pebbled bases with compact code blocks are typical of mid-century packaging bottles.

Common U.S. glassmaker logos you’ll encounter:

• Owens-Illinois: An “I” within an “O” (earlier within a diamond, later without). Typically, plant code to the left, date code to the right, and additional mold numbers nearby. Early date codes can be single digits (decade inference required), while later codes are two-digit years. Treat dots and ancillary marks cautiously; practices shifted over time.
• Hazel-Atlas: An “H” over an “A” monogram; widely used for tableware and containers (1920s–1960s).
• Anchor Hocking: An anchor with an “H,” used from the late 1930s onward.
• Ball (fruit jars): Distinct script styles and word arrangements evolved over decades; the script style itself is often diagnostic.
• Whitall Tatum: “WT,” “W.T. & Co.,” or spelled-out marks; prolific in medicine and pharmacy bottles in the 19th and early 20th centuries.
• Illinois Glass, Brockway, Knox, and other regional makers: Various initials and monograms. Local plant histories help contextualize codes.

What not to assume:

• Lone numbers on the base are usually mold/cavity numbers, not dates.
• “8,” “12,” “16” often denote fluid ounces. Don’t treat them as years.
• A maker’s logo date code applies to the glass manufacture, not necessarily the product’s brand launch year.

Seams And Finishes: Hand-Blown vs Machine-Made

Mold seams and lip finishes are quick dating tools when base marks are absent or ambiguous.

Mold seams:

• No mold seam (free-blown) or seams that are faint and irregular: Early hand production.
• Seam stops below the lip: Hand-finished top on a molded body. Common through the late 19th century. The lip (finish) may be applied (extra glass added and tooled) or tooled from the neck glass.
• Seam runs through the lip: Machine-made. Automatic machines proliferated from the 1910s onward. By the 1920s–1930s, most mass-market bottles in the U.S. were machine-made.

Finish types and dating hints:

• Blob top and applied finishes: Frequent on mid-19th to late-19th-century sodas, beers, and bitters.
• Lightning stopper (swing-top): Late 19th into 20th century, widely reused on beer/mineral water.
• Crown finish: Patented 1892, dominant for crown-capped sodas and beers by the early 20th century.
• Continuous-thread (screw) finishes: Exist in the 19th century, but widespread in food, pharmaceutical, and household bottles in the 20th.
• Ground lips: Seen on fruit jars and tableware; a ground sealing surface points to jar-type containers of various eras.

Other surface tells:

• Whittle marks (subtle, wavy undulations): Mold or cooling artifacts typical of earlier bottle glass; often imitated in reproductions but generally finer and more random in authentic pieces.
• Seed bubbles and stretch marks: Common in hand-made glass; machine glass tends to be more uniform.

Numbers, Patents, And “Warnings”: Decoding Non-Logo Marks

Not all marks are logos, and misreading them can derail an appraisal.

Capacity and content statements:

• “FULL PINT,” “ONE QUART,” and “CONTENTS 12 FL OZ” are utility markings, not dates.
• Apothecary graduations can appear on panels or shoulders; check if they’re functional (accurate spacings) or decorative.

Property and legal statements:

• “THIS BOTTLE NOT TO BE SOLD” or “NOT TO BE REFILLED”: Common on late-19th to early-20th-century soda, beer, and dairy bottles. Indicates reuse loop and brand control, not the exact year.
• “FEDERAL LAW FORBIDS SALE OR RE-USE OF THIS BOTTLE”: U.S. liquor bottles (roughly 1935–1964). A reliable date bracket for spirits containers in that period.
• “RETURN FOR DEPOSIT”: Mid-20th-century reuse programs.

Patent and design references:

• “PATENTED” with a date: The patent belongs to the closure, finish, mold, or design. It bracketing the earliest possible use; production may continue decades after.
• “MASON’S PATENT NOV 30TH 1858”: Embossed on fruit jars for many decades. This is a pattern date, not necessarily the jar’s production year.
• Design patent numbers (beginning with a “D”) and utility patent numbers can be looked up offline; for field work, treat them as earliest-use anchors.

Code clusters:

• Plant codes and mold numbers are usually grouped near a logo on the base. Learn your region’s major plants so you can separate maker from brand.
• European and Canadian bottles have distinct coding conventions; be alert to country of origin clues in language and spelling on the body (“Litre,” “Trade Mark Registered,” bilingual labels).

Color and composition cues that support the reading:

• Aqua, emerald, olive, and amber dominate the 19th century; cobalt appears across eras but is strongly associated with certain medicines and poisons.
• Manganese-decolorized glass can turn amethyst with prolonged UV exposure; deep purple can also result from artificial irradiation. Artificial color change usually lowers value and can be spotted by uniform, intense hue inconsistent with wear.
• Selenium/arsenic decolorizers (common in the 20th century) can warm to straw tones when irradiated; not a dating tool by itself but useful context.

Field Checklist For Reading Bottle Marks

• Clean gently first: Use warm water, mild soap, and a soft brush to expose fine embossing. Avoid abrasives that create “sick” glass.
• Map the bottle: Note height, capacity, body shape, base profile, finish type, and color.
• Start at the base: Photograph and sketch the base, capturing any logos, numbers, scars, or stippling.
• Identify manufacturing method: Follow mold seams. Do they pass through the lip? Note pontil or suction scars.
• Read logos before numbers: Separate maker’s mark from capacity and mold codes.
• Decode cautiously: Treat lone digits as mold/cavity numbers unless paired with a clear maker logo and date code format.
• Bracket with legal text: “Federal Law Forbids…” dates liquor bottles to roughly 1935–1964; use it as a cross-check, not a sole proof.
• Cross-check finish type: Does the lip style align with the supposed era? A crown finish on a piece “dated” 1870 is a red flag.
• Look for brand/proprietor embossing: City and proprietor names can lead you to directory years for tighter dating.
• Beware of “sun-purpled” glass: Attractive, but often man-induced in modern times; note it in appraisals.
• Document condition separately: Chips, stain, internal haze, and grinding don’t change the date, but they affect value; keep facts distinct.
• Record provenance: Find location, dig context, or family history can corroborate a time frame.

FAQ: Old Bottle Marks

Q: I found a single number on the base. Is that the year? A: Usually not. Single or small-number clusters typically indicate mold cavity numbers or size codes. A year is more plausible when paired with a recognizable maker’s logo that uses standardized date coding.

Q: Does a pontil scar always mean the bottle is valuable? A: No. A pontil scar indicates hand production, generally earlier than machine-made bottles, but value depends on category desirability, rarity, condition, color, and embossing. Common pontiled utilities can be modest in value; rare pictorial flasks can be significant.

Q: How do I tell if a date code is 1934 or 1944 when it’s a single digit? A: Context. Look at the logo style (earlier vs later), presence of brand/legal text (“Federal Law Forbids…” suggests mid-century), finish style, and packaging norms. Some makers changed date coding practices over time, so avoid firm assertions without corroboration.

Q: The bottle is amethyst. Is it naturally that color? A: Maybe. Some glass was intentionally colored amethyst. However, many clear bottles containing manganese turn purple after UV exposure or artificial irradiation. Uniform, intense purple on a bottle that should be clear is a caution sign.

Q: What’s the fastest way to separate a reproduction from an antique? A: Compare the story told by seams, finish, and base. Repros often have mismatched cues (e.g., crude “pontil” on a bottle with machine seams, or historically incorrect finish types). The glass surface on reproductions can look uniformly glossy with simplified embossing and minimal wear in friction points.

Practical takeaways: Read the base first, confirm with seams and finish, and let legal text and brand embossing refine the bracket. Treat numbers as codes until proven dates, and always document your reasoning. With repetition, you’ll recognize logos and code layouts at a glance and build faster, defensible appraisals.