If you collect antique bottles (or you just dug one up in a garden), the fastest way to get oriented is to flip it over. The bottom markings on an old glass bottle often tell you how it was made, who made it, and sometimes even when.
This guide is built for real-world identification. We’ll walk through the most common bottle-bottom clues — pontil scars, Owens suction scars, maker logos, date codes, mold numbers, and “blank” bases — then show how to turn those clues into a defensible age range and valuation.
Two-step intake
Share your antique bottle details with an expert today
Upload your bottle photos and we’ll confirm age range, maker clues, and current market value — with a written quote and next steps.
We store your intake securely, sync it with the Appraisily CRM, and redirect you to checkout to reserve your slot.
Gallery: common bottle-bottom clues at a glance
These examples match the terms you’ll see in collector forums and identification guides. Use them as visual anchors, then cross-check against your bottle.
Step 1: Photograph the base so the mark reads clearly
Before decoding anything, make sure you’re reading the mark correctly. Glass is reflective, embossing can be shallow, and dirt can hide key details. A five-minute photo routine can save hours of wrong turns.
- Use raking light: hold a flashlight almost parallel to the surface to make embossing pop.
- Shoot straight-on: keep the camera centered over the base to avoid distortion.
- Photograph seams too: take one photo of the base and one of the neck/lip to show how high seams run.
- Capture the whole bottle: shape, color, and closure type can confirm or contradict the base clues.
Step 2: Read the “scar” — handmade vs. machine-made
The single strongest dating clue on many bottles is the mark left by how the bottle was held or released during manufacturing. Collectors often call this the base scar.
- Pontil scar (rough, sometimes glassy, often irregular): a sign of hand production. Pontil types vary (open pontil, iron pontil, sand pontil) and should be interpreted with other features.
- Owens suction scar (clean circle): associated with the Owens Automatic Bottle Machine era and later machine production.
- Valve / ejection mark (other shapes): later machines can leave different base patterns.
Tip: a bottle can be machine-made but still look “old.” That’s why the scar should be paired with seam behavior and finish.
Step 3: Use mold seams as a cross-check
Mold seams are the “second opinion” that keeps you honest. On many U.S. bottles, a seam running all the way through the lip suggests a later, fully-machine finish, while an older applied finish often interrupts or hides the seam near the top.
- Seams stop below the lip: can indicate an applied finish or an earlier manufacturing step.
- Seams run through the lip: more common on later machine-made bottles.
- Three-piece molds: can leave distinct heel lines and seam patterns.
Step 4: Identify the maker mark (logo or initials)
A maker logo is a manufacturer clue, not a date by itself. Once you have a likely maker, you still need to interpret the rest of the evidence (scar, seams, finish, bottle type) to land on a credible date range.
Common 20th-century patterns you’ll see on bases:
- Owens-Illinois: often an “O in a diamond” motif; date/plant codes vary by era.
- Hazel-Atlas: “H” over “A” monogram on many bottles and jars.
- Anchor Hocking: anchor/letter marks; used across a broad product line.
- Ball / Kerr / Mason jar marks: common on canning jars; base marks differ from bottle marks.
If the bottle is embossed on the side (e.g., a pharmacy name, soda bottler, or bitters brand), the base mark may identify the glass maker while the side embossing identifies the customer.
Step 5: Decode numbers and letters (mold, plant, capacity)
Numbers on the bottom are frequently misunderstood. In many cases they are internal manufacturing codes: mold number, cavity number, plant code, or capacity mark. They rarely translate to “this is the 12th bottle made in 1912.”
- Mold/cavity numbers: used for quality control and mold tracking; can be repeated across years.
- Plant codes: sometimes identify a manufacturing location (varies by company and era).
- Capacity: common on food/medicine bottles (e.g., ounces or milliliters), sometimes abbreviated.
- Patent dates: can indicate a not-earlier-than date, but bottles may be produced long after the patent.
Step 6: What if the bottom is blank?
A blank base doesn’t mean the bottle is modern — it usually means the maker relied on other identifiers (shape, label, embossing) or the manufacturing method didn’t require a base mark. In those cases, prioritize:
- Glass color: aqua, amber, cobalt, milk glass, and “black glass” each have different market patterns.
- Closure & finish: blob top, crown top, screw top, applied lip, and tooled lip help narrow era.
- Texture clues: turn-mold swirling can point to earlier production even when the base is plain.
Step 7: Translate identification clues into value
Two bottles can share the same maker mark and still sell for very different prices. Value is driven by a combination of scarcity and a “collector story.” Here’s what tends to move prices most:
- Rarity of the bottle type: bitters, pictorial flasks, and regional sodas often outperform common utilities.
- Condition: chips on the lip and base wear can materially reduce value.
- Color and desirability: unusual colors or strong amber/aqua tones can command premiums.
- Embossing and provenance: named pharmacies, towns, or historically tied bottles can be standout lots.
Step 8: Anchor your estimate with sold auction comps
Asking prices online are often “wish prices.” Sold auction results show what buyers actually paid. Below are recent examples pulled from
the Appraisily auction dataset /mnt/srv-storage/auctions-data/antique-bottles/.
| Lot | Auction house | Date | Result (hammer) | Why it matters |
|---|---|---|---|---|
| 2047 | Holabird Western Americana | 2023-03-04 | $1,150 | Provenance-driven group lot (SS Central America treasure) illustrates premium “story value.” |
| 518 | Rafael Osona Auctions | 2024-08-24 | $900 | Mixed lot (bitters/gin/flasks) shows how quality assortments can outperform singles. |
| 19 | Searchlight / Saucon Valley Auctions | 2024-01-14 | $550 | Decorative/etched bottles can trade like folk art; scarcity and aesthetics matter as much as marks. |
Step 9: Common mistakes when reading bottom marks
- Dating from the logo alone: many marks were used for decades; always cross-check seams and finish.
- Confusing patent dates with manufacture dates: the bottle can be later than the patent.
- Assuming numbers equal year: “12” is more often a mold/cavity code than 1912.
- Skipping the lip photo: whether seams run through the lip can change the date range dramatically.
When to get an expert appraisal
If your bottle has a strong pontil scar, unusual color, pictorial embossing, or compelling provenance (estate history, excavation site, shipwreck context), the value range can widen quickly. A short written appraisal can confirm identity, establish condition notes, and point to the right selling channel.
Search variations collectors ask
Readers often Google:
- how to identify antique bottle markings on the bottom
- what does a pontil scar look like on a glass bottle
- how to date a bottle with an Owens suction scar
- Owens-Illinois bottle date code chart by year
- what do numbers on the bottom of a glass bottle mean
- how to tell hand blown vs machine made bottle
- are unmarked glass bottles antique
- how to identify turn mold glass bottles
- where to get an antique bottle appraisal near me
Each question is answered in the identification guide above.
References & data sources
-
Appraisily auction dataset:
/mnt/srv-storage/auctions-data/antique-bottles/(accessed 2025-12-17). Comps cited from Holabird Western Americana lot 2047 (2023-03-04), Rafael Osona Auctions lot 518 (2024-08-24), and Searchlight / Saucon Valley Auctions lot 19 (2024-01-14). - Society for Historical Archaeology (SHA) glass bottle identification resources: https://sha.org/resources/glass-bottles/.
- BottleBooks (reference guides for bottle identification and logos): https://bottlebooks.com/.