{"id":5788,"date":"2026-08-03T09:25:00","date_gmt":"2026-08-03T13:25:00","guid":{"rendered":"https:\/\/jbtopglass.com\/?p=5788"},"modified":"2026-08-02T22:46:32","modified_gmt":"2026-08-03T02:46:32","slug":"glass-bottle-bottom-numbers","status":"publish","type":"post","link":"https:\/\/jbtopglass.com\/ar\/knowledge\/glass-bottle-bottom-numbers\/","title":{"rendered":"How to Read the Numbers on the Bottom of a Glass Bottle?"},"content":{"rendered":"\n
\"glass<\/figure>\n\n\n\r\n
<\/div>\n\n\n

Glass bottle bottom numbers may identify the mold cavity, manufacturer, production plant, date code, capacity, or glass material. Raised dots can also identify the mold that formed the bottle. Printed numbers are different and often belong to the filling company\u2019s batch or date system.<\/p>\n\n\n\n

There is no universal way to read every bottle. A single \u201c7\u201d could be a cavity number on one bottle and part of a date code on another. Its meaning depends on the nearby logo, letters, measurement units, symbols, position, and the coding system used by that manufacturer.<\/p>\n\n\n\n

What Do Glass Bottle Bottom Numbers Mean?<\/h2>\n\n\n\n

Most bottle-bottom marks fall into a few practical groups. Some help the glass factory trace production. Others state capacity or identify the packaging material. Marks on old bottles may also help collectors estimate when and where a bottle was made.<\/p>\n\n\n\n

Mark on the Bottle<\/th>Common Meaning<\/th>Can It Be Read Alone?<\/th><\/tr><\/thead>
One or two raised digits<\/td>Mold or cavity number<\/td>Usually not<\/td><\/tr>
Raised dots near the heel<\/td>Machine-readable cavity code<\/td>No<\/td><\/tr>
Logo or initials<\/td>Glass manufacturer<\/td>Sometimes<\/td><\/tr>
Digits around a maker\u2019s mark<\/td>Plant, date, mold, or product code<\/td>Only with the maker\u2019s system<\/td><\/tr>
Number followed by ml, cl, or mm<\/td>Capacity or fill-level information<\/td>Usually<\/td><\/tr>
GL 70, GL 71, or GL 72<\/td>Glass material and color category<\/td>Yes<\/td><\/tr>
Printed or laser code<\/td>Filling date, lot, line, or product traceability<\/td>Only with the filler\u2019s records<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

The layout matters as much as the characters. Two identical numbers placed on opposite sides of a logo may have different meanings. A number followed by \u201cml\u201d is much easier to interpret than the same number standing alone.<\/p>\n\n\n\n

\"common<\/figure>\n\n\n\n

How Do You Read the Marks Step by Step?<\/h2>\n\n\n\n

1. Check Whether the Mark Is Molded or Printed<\/h3>\n\n\n\n

A molded mark is raised or recessed as part of the glass. It was formed when the hot glass contacted the mold. These marks commonly relate to the container manufacturer, mold, cavity, capacity, or material.<\/p>\n\n\n\n

An inkjet, laser, or printed code is added later and may identify a filling batch, line, production time, or best-before date. Do not use it automatically to date the glass itself.<\/p>\n\n\n\n

2. Find the Logo, Letters, and Units<\/h3>\n\n\n\n

Look for a maker\u2019s logo or initials before trying to interpret the digits. Also record any units such as ml, cl, or mm and symbols such as a reversed epsilon. These details can turn an uncertain number into a capacity or manufacturing mark.<\/p>\n\n\n\n

Use side lighting and rotate the bottle until the characters are upright. Curved glass and stippling can make a 3 look like an 8 or turn a logo into an apparent number.<\/p>\n\n\n\n

3. Record the Position of Every Mark<\/h3>\n\n\n\n

Record what appears above, below, left, and right of the logo. Do not rearrange the characters into one long number. Position can determine whether a digit represents a plant, year, or cavity.<\/p>\n\n\n\n

4. Match the Complete Pattern to a Reliable Source<\/h3>\n\n\n\n

For a modern bottle, use the technical drawing or ask the glass manufacturer. For a historic bottle, compare the complete logo and layout with a specialist reference. The Society for Historical Archaeology explains that a maker\u2019s mark can help identify origin and age<\/a>, but only when the period of use is known.<\/p>\n\n\n\n

Are One- or Two-Digit Numbers Usually Mold Numbers?<\/h2>\n\n\n\n

Often, yes. Modern bottle-forming machines use several sections and cavities at the same time. Each cavity can leave its own number or code on the bottle. If inspection finds a repeated defect, the factory can connect the affected bottles to the mold that produced them.<\/p>\n\n\n\n

The code may appear as a raised number, a combination of letters and numbers, or a row of small dots. A European patent describing container inspection states that raised dots on the lower part of a bottle can identify the forming-machine section and its specific mold cavity<\/a>.<\/p>\n\n\n\n

Two bottles of the same design may therefore carry different small numbers. They may simply have come from different cavities on the same production line.<\/p>\n\n\n\n

\"different<\/figure>\n\n\n\n

Does a Bottom Number Show the Bottle\u2019s Date or Factory?<\/h2>\n\n\n\n

It can, but not without context. Some manufacturers combine a logo with plant and date codes. Others use separate internal systems, change the format over time, or do not place a readable date on the base at all.<\/p>\n\n\n\n

A well-documented historical example shows why position matters. The Society for Historical Archaeology identifies an Owens-Illinois beer bottle with plant code \u201c20\u201d to the left of the maker\u2019s mark and date code \u201c1\u201d to the right. Other evidence connects that bottle to the Oakland plant in 1941. The same digit \u201c1\u201d without the logo and layout would not prove the year.<\/p>\n\n\n\n

Never assume that a two-digit number such as \u201c74\u201d must mean 1974. It could be a mold, catalog, plant, capacity, or design code. First identify the manufacturer, then find the code system used during the likely production period.<\/p>\n\n\n\n

What Do Capacity Numbers and the Reversed Epsilon Mean?<\/h2>\n\n\n\n

Capacity marks are easier to read when a unit appears beside the number. A bottle may show its nominal capacity in millilitres, centilitres, or litres. Another number may refer to brim capacity or to the distance between the brim and the intended fill level.<\/p>\n\n\n\n

Under the EU rules for measuring container bottles, compliant bottles carry a reversed epsilon symbol. The same rules require the nominal capacity and the manufacturer\u2019s identifying mark. The bottom or bottom rim can also show the brim capacity in centilitres, or the fill-level distance in millimetres. The official EU measuring-container directive<\/a> defines these markings.<\/p>\n\n\n\n

For example, \u201c75 cl\u201d can state a nominal capacity, while a separate number followed by \u201cmm\u201d can specify the designed distance from the brim to the filling level. A bare number should not be treated as capacity unless its unit, symbol, drawing, or manufacturer information supports that reading.<\/p>\n\n\n\n

The reversed epsilon on the glass should not be confused with the \u201c\u212e\u201d mark printed beside a declared quantity. The reversed epsilon relates to a measuring container bottle. The \u201c\u212e\u201d mark<\/a> is a declaration by the packer under the average quantity system.<\/p>\n\n\n\n

If a base mark refers to maximum internal volume, it is also important to distinguish the normal declared fill from brimful or overflow capacity<\/a>.<\/p>\n\n\n\n

What Do GL 70, GL 71, and GL 72 Mean?<\/h2>\n\n\n\n

These are packaging-material identification codes, not years. The system established by EU Commission Decision 97\/129\/EC assigns:<\/p>\n\n\n\n