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Estimating the age of antique bottles can sometimes be a difficult task even for the experienced collector. However, by following some basic guidelines anyone can determine approximate age. Although this brief article is primarily intended for American-made bottles, glass from other countries has evolved similarly. This outline covers basic patterns but note that there are exceptions to every rule.

Mold Seam

Most bottles produced in the past 150 years were formed by blowing molten glass into a mold. Molds were made of iron or wood and consist of 2 or 3 pieces. When the bottle was removed from a mold, a faint seam remained in the glass, running from the base to a point somewhere between the shoulder on up to the top edge of the mouth. In a 3-piece mold, a seam often runs horizontally around the shoulder of the bottle with opposing seams on the neck.

To some extent, the height of the mold seam on the bottle can indicate age. However, there are plenty of exceptions to any kind of “thermometer” rule (ie. the higher the seam goes, the newer the bottle.)

Entire classes of bottles break the rule. For example, fruit jars made in the third and forth quarters of the 19th century. Sheared top bottles are another case where mold seam height is not a good indicator of age.

See the Mold Seam Examples page for more details [coming soon]

Base of Bottle

Pontil mark – A iron rod was often stuck to the base of hand blown bottles prior to approximately 1860. This allowed an assistant to hold the bottle while a glassblower would attach and finish the lip of the vessel. When the bottle was broken or sheared, a ring or area of rough glass or grey graphite remained. The pontil is a definitive mark that dates glass. Be aware that reproductions can have smooth, molded pontil marks or sometimes an authentic looking jagged mark.

Numbers and Letters- Such markings on the base indicate late 19th century to present time day manufacture. Occasionally, you will see base embossing of patent dates or the classic Rickets Patent of mid-19th century era.

Wheaton – Indicates glass made at the Wheaton Glassworks in southern New Jersey. This company was prolific in its production of reproduction and other antique-looking bottles and glass which they produced in the mid 20th century to the present.

CB – Stands for Clevenger Brothers, glassblowers also from New Jersey who produced high-quality reproduction glass. Owens bottle ring- During the period of 1890 to 1910, Micheal Owens developed automated methods for opening and closing bottle molds which led to mass production of glass and bottles. A distinctive characteristic of wares made by this method is a thin embossed circle on the base of the bottle, usually found with numbers and other marks indicating year of manufacture, mold number, etc. Bottles with such markings date from approximately 1910 to 1960

Other Guidelines

Specific embossing found on bottles can be an immediate indication of age. Liquor bottles produced after Prohibition (after 1930) are found with the embossing “Federal Law Prohibits Sale or Reuse of this Bottle.” Bottles marked “Wheaton” on the base are probably reproductions made by Wheaton Glassworks in New Jersey in the 20th century. Other common markings include “W.T. Co.” which stands for Whitall Tatum, a turn of the century glass manufacturer. An entire book called Bottle Makers and Their Marks by Toulouse documents the hundreds of markings made by glass manufacturers.


Don’t assume that the old bottle you have is necessarily old or antique. There are a lot of reproduction bottles out there, and new ones that look old are made every day. Modern bottles are sometimes intentionally made to look old and mimic the shape, surface texture and overall appearance of hand blown glass.
Be wary of bottles that have dates on them such as 1776 or others prior to 1850, since dated bottles prior to this time are rare. Bold and garish colors are also rare in antique bottles, so beware of bright reds, greens, yellows and purples. If it looks too good to be true, it probably is!
Bottles that are made to look old often are exaggerated in their “handmadeness”. There are huge numbers of bubbles and impurities in the glass. The glass itself is commonly thick, heavy and distorted in shape. Early glassmakers tried their best to make uniform, quality wares; modern makers try hard to make their bottles look handblown.

Mouth of Bottle

Perhaps the most obvious key to age is the mouth of the bottle. As a general rule, screw top bottles (except canning jars) were made after 1910 or so. Cork top bottles generally vanished at the turn of this century. Look closely at the mold seam and where the lip meets the bottle. All truely hand blown bottles have an applied lip. The curious student of glass items will quickly learn when a lip has been formed onto the bottle and when it was applied by hand. Handwork in glassblowing disappeared in the late 19th century. It is a safe rule that after 1890, few, if any, bottles were mass-produced with an applied lip.

There’s no substitute for experience

Take some time to talk with a bottle collector at a local club or show. Examine as many old bottles as you can and ask lots of questions. You will find that you can quickly train your eye to know a lot about the age of most bottles that you will find.