How to Date an Old Whisky Bottle

“26 2/3 Fl. Oz.” is a small inscription with a long history: it was the standard UK bottle size until the end of the 1970s, according to Whisky.Auction.[1] On an old whisky bottle, details like this can help establish a likely bottling date range.

The strongest dating comes from reading those details together. Compare volume, strength notation, glass markings and label wording to build that range. Whisky.Auction recommends considering the label, wording, closure, condition and bottle code as a whole.[2]

Start with a record of the bottle

Photograph first, interpret second. Take clear pictures of the front, back, neck, closure and base, then transcribe the volume and strength exactly. Preserve distinctions such as “26 2/3 Fl. Oz.”, “75cl”, “70cl”, “proof” and “% ABV”. Record embossed lettering separately from printed or laser markings: they are different kinds of evidence.

Work through the bottle in this order:

1. Record its wording and markings without assigning dates.
2. Identify the market indicated by the label before interpreting proof or volume.
3. Compare each feature with a dated source.
4. Find the period in which the supported date ranges overlap.
5. Write a conclusion that separates strong evidence from supporting clues.

Keep photographs beside your notes so another reader can check both the transcription and the interpretation. For printed production markings, consult bottle codes and batch numbers alongside the historical clues below.

How to date an old whisky bottle by its volume

Bottle size is a useful first clue, provided you know the intended market. Whisky.Auction describes UK bottles from the 1940s to the 1960s as often carrying no size statement. Where “26 2/3 Fl. Oz.” appears, it represents 757 ml (75.7 cl), the standard size until the end of the 1970s.[1]

Imperial and metric measures appeared together towards the end of the 1970s. By the 1980s, UK bottles were fully metric, with 75.7 cl rounded to 750 ml (75 cl). The next shift brought 700 ml (70 cl) as the standard across Europe in the early 1990s.[1]

The change to 70 cl took time. A European Commission report dated 12 October 1992 states that “Scotch whisky producers are reducing the size of their bottles from 75cl to 70cl”. That is a transition in progress, so a 70 cl label does not automatically mean “bottled after 1992”.[5]

The legal timetable is distinct from the packaging history. The UK’s Weights and Measures (Intoxicating Liquor) Order 1988 came into force on 1 January 1989. Its explanatory note says spirits were added to the prescribed quantities list with effect from 1 January 1992. These are useful legal milestones, rather than dates for the entire commercial change.[4]

Read US volumes in their own context

For US bottles, the key instruction is explicit. TTB Industry Circular 79-07 required metric standards of fill to apply “without exception, after December 31, 1979”. In this dating framework, a 750 ml statement therefore points towards 1980 or later.[6]

Volume alone does not identify an American destination. UK bottles also used 75 cl during the 1980s, while current US federal standards permit both 750 ml and 700 ml containers.[1][7] Establish the market from the label before using either size to narrow the date.

Proof marks and alcohol strength

Read the proof system before reading the number. UK proof and US proof use different calculations: Whisky.Auction gives the UK conversion as proof divided by 1.75, while US proof is divided by two.[1]

Its rounded UK examples are:

These conversions apply to UK proof, not US proof.[1] Most importantly, “70 proof” does not mean 70% ABV.

The UK’s move away from proof has a firm legal date. The Alcoholic Liquors (Amendment of Enactments Relating to Strength and to Units of Measurement) Order 1979 came into operation on 1 January 1980. It replaced the proof system with percentage alcohol by volume under the OIML system, measured at 20 degrees Celsius.[3]

Whisky.Auction accordingly treats a UK strength expressed in degrees proof as pointing towards the 1970s or earlier.[1] This is a valuable dating clue to set beside the volume, label and glass, rather than an exact bottling date derived from the legislation.

Keep three entries in your notes: the wording on the bottle, the system it uses and the date range the source suggests. That simple separation prevents an accurately copied number from being misread later.

Historic tax strips and UK duty stamps

US and Italian tax strips

A surviving tax strip deserves its own photograph. Whisky.Auction identifies these strips principally with bottles intended for the US and Italian markets.[2] Capture the wording and position, then assess the strip separately from the volume and strength.

For the United States, the statutory milestone is the repeal of 26 USC 5205, concerning stamps for distilled spirits containers. The repeal was enacted on 18 July 1984 and took effect on 1 July 1985.[8]

The distinction matters: enactment and effect are different dates. Use the effective date when assessing the historical scheme, but do not assign a bottling year from the repeal alone. Compare the strip with the rest of the bottle.

UK duty stamps

Record UK duty stamps separately from historic overseas tax strips. Similar appearances can conceal different schemes, so photograph the marking and transcribe all visible wording before interpreting it.

A useful dating source must identify the particular scheme and explain its relevant dates. Until that evidence is available, leave the stamp’s interpretation open. The bottle’s independently supported volume, strength and glass clues can still move the investigation forward without assigning the stamp a premature date.

Look underneath: glassmaker marks and base codes

Turn the bottle over. Its base may offer the clearest lead when the label says little: Whisky.Auction finds base codes especially useful on export bottles without imperial measures.[2]

The auction house identifies “U G B” as the mark of United Glass Bottle Manufacturers, used until the end of the 1960s. An “S” to the left of the code identifies the company’s Sherdley factory.[2]

For that particular sequence, it gives:

Read the whole arrangement, including the surrounding symbols. These associations apply to the identified glassmaker’s markings, not to every bottle bearing similar letters.[2] A convenient pair of characters means less than the complete pattern in which it appears.

For example, a bottle with “U G B” underneath and UK proof on its label would offer compatible clues: the mark was used until the end of the 1960s, while UK proof points towards the 1970s or earlier. Together they support an earlier period, without making the glass mark an exact bottling date.[1][2]

WhiskyAuction.com also publishes a glass bottle code table covering makers including Lax and Shaw, Allied Glass Containers, United Glass and Owens-Illinois, citing glassbottlemarks.com.[12] It is a useful comparison reference; keep an auction house’s published identification distinct from an independently verified date in your notes.

Royal warrants: useful supporting evidence

A royal warrant offers a historical clue, with a built-in allowance for continued use. The Royal Family describes warrants as initially granted for up to five years. The Royal Warrant Holders Association says that when a Grantor dies, the warrant becomes void, although the holder may usually continue displaying the Royal Arms for up to two years.[10][11]

Photograph the complete warrant wording, including any reference to a late monarch. A monarch’s name can help place the bottle, but those rules mean it cannot simply supply a bottling year.

Compare the royal reference with the volume statement and glass markings. If they disagree, investigate the disagreement rather than allowing the apparent precision of a name to settle the question. A convincing date range explains the whole bottle, not just its most decorative feature.

Common mistakes when dating a bottle

Most dating errors begin when a useful clue becomes a universal rule. Keep these distinctions visible in your working notes:

• “70 proof means 70% alcohol.” Proof is not a percentage. In the UK system, 70 proof is approximately 40% ABV.[1]
• “75 cl means American.” UK bottles also used 75 cl in the 1980s.[1]
• “Every 70 cl bottle dates from after 1992.” The change was a transition, not a single cutoff. The October 1992 Commission report describes it as ongoing.[5]
• “A royal warrant supplies the year.” Royal Arms could remain in use for a permitted period after a Grantor’s death.[10]

Use “consistent with” or “probably” where appropriate, and leave unresolved contradictions visible in the conclusion.

Where to go next

• How to Research a Bottle's History: build a documented investigation around the physical evidence.
• Distillery Bottlings vs Independent Bottlings: identify which kind of bottling you are examining.
• Core Range, Limited Release and Discontinued Whisky: understand the release descriptions encountered during research.

Sources

[1] Whisky.Auction magazine. How To Date A Bottle, Part 1. Undated web article, auction house’s account, version supplied as checked November 2026. https://magazine.whisky.auction/how-to/how-to-date-a-bottle/

[2] Whisky.Auction magazine. How To Date A Bottle, Part 2. Undated web article, auction house’s account, version supplied as checked November 2026. https://magazine.whisky.auction/how-to/how-to-date-a-bottle-part-2/

[3] legislation.gov.uk. The Alcoholic Liquors (Amendment of Enactments Relating To Strength and To Units of Measurement) Order 1979. SI 1979/241, original text, 1979. https://www.legislation.gov.uk/uksi/1979/241/made/data.html

[4] legislation.gov.uk. The Weights and Measures (Intoxicating Liquor) Order 1988. SI 1988/2039, 1988. https://www.legislation.gov.uk/uksi/1988/2039

[5] Commission of the European Communities. Report to the Council on the alcoholic strength at which whisky is released to the market. 12 October 1992. https://aei.pitt.edu/9175/1/9175.pdf

[6] TTB. Industry Circular 79-07. 2 July 1979. https://www.ttb.gov/public-information/industry-circulars/archives/1979/79-07

[7] eCFR. 27 CFR 5.203 Standards of fill (container sizes). Current text supplied as checked November 2026. http://ecfr.gov/current/title-27/chapter-I/subchapter-A/part-5/subpart-K/section-5.203

[8] Office of the Law Revision Counsel. 26 U.S.C. 5205: Repealed. Repeal enacted 1984, effective 1985. http://uscode.house.gov/us/usc/t26/s5205/

[10] Royal Warrant Holders Association. Frequently Asked Questions. Undated web page, version supplied as checked November 2026. https://www.royalwarrant.org/frequently-asked-questions

[11] The Royal Family. Royal warrants. Undated web page, version supplied as checked November 2026. https://www.royal.uk/royal-warrants

[12] WhiskyAuction.com. Whisky Glass Bottle Codes at the bottom. Undated reference table, auction house’s account, version supplied as checked November 2026. https://www.whiskyauction.com/node/1911925

This desk research draft uses the supplied verified fact sheet, distinguishing auction house interpretations from the legal instruments and institutional guidance it cites.

Last checked: November 2026