Bench&Brace

Identification

Reading Casting Marks and Numbers on Old Iron

What the raised letters, numbers and symbols cast into a tool actually mean - model numbers, foundry marks, pattern numbers and patent dates - and which ones can date a tool.

  • updated 2026-02-14
  • 4 min read
On this page

Turn almost any piece of old cast iron over and you will find raised or incised marks: a number, a letter, sometimes a date. People routinely read all of them as model numbers, which is why so many identification questions start from the wrong premise.

There are four different kinds of mark and they mean four different things.

1. Model numbers

The number the manufacturer sold the tool as. On Stanley planes this is usually cast into the toe or the bed, or stamped into the wooden body on a transitional.

This is the one you want, and it is often the hardest to find because it is the one most likely to be worn, painted over or filled with rust.

2. Pattern and foundry numbers

Numbers used inside the factory to keep track of which mould made which casting. They appear in odd places — inside the body, under the frog, on the back of a lever cap — and often have letters attached.

These are not model numbers and looking them up will get you nowhere. If a number is in an unmachined interior surface and does not match any catalogued model, it is almost certainly a pattern number.

They are still useful for one thing: a pattern number that matches between two parts is decent evidence the parts belong together.

3. Patent dates

Dates cast into the metal, usually in a compressed form like PAT. AUG-19-02 or a bare APL-19-92.

A patent date is a floor, never a ceiling. It says the casting was made after the patent was granted. Manufacturers kept the same date on the pattern for years, sometimes decades, and sometimes after the patent expired. A plane carrying only 1902 patent dates may well have been made in 1918.

What patent dates are genuinely good for is counting. Manufacturers added dates as new patents were granted, so the number of dates present narrows the window. On Stanley bench planes, three dates behind the frog is the classic 1910–1918 signature.

If you want to run one down properly, search the date and the inventor on a patent database. US patents are not subject to copyright, and the drawings are often the best documentation of how a mechanism was meant to work — frequently better than anything the company published.

4. Country and trademark marks

MADE IN USA, MADE IN ENGLAND, a company name, a trademark symbol. These respond to trade law and corporate history rather than product design, which makes them unusually reliable dating tools.

MADE IN USA on a Stanley bench plane bed means 1931 or later, full stop. A company name that stopped being used in a known year caps the tool at that year. These are the hardest marks to argue with, because the company had a legal reason to change them on a specific date.

Reading marks you can barely see

Old castings are worn, painted and rusty. Some things that help:

  • Raking light. A single light source almost parallel to the surface throws shadows off raised letters that flat light washes out. This alone solves most cases.
  • A rubbing. Thin paper and the side of a pencil, same as a gravestone. Works on incised marks that raking light cannot help with.
  • Chalk or talc. Dust the surface and wipe it back; powder stays in the recesses.
  • Do not clean first. People wire-wheel a casting to read a mark and remove the mark. Try the light and the paper before any abrasive touches it.

When the mark and the tool disagree

Regularly, a tool will carry a mark that does not fit anything else about it. Before concluding you have found an undocumented variant, work through the ordinary explanations:

  1. It is a pattern number, not a model number.
  2. The part is not original to the tool.
  3. The tool is a private-label version — Sears, Winchester, Keen Kutter and dozens of hardware chains sold rebadged tools made by the big manufacturers, with different numbers cast in. A tool that looks exactly like a Stanley but carries a strange name and number probably is a Stanley, made under contract.
  4. It is a later reproduction of a discontinued pattern.

Genuine undocumented variants do exist and finding one is a good day. They are just much rarer than the four explanations above.

Where to check what you have found

Cross-reference before you conclude. The community reference sites cover the main US makers model by model, and the scanned-literature libraries hold catalogues and manuals for machinery that no reference book covers.

Forum identification threads are useful for spotting variants nobody catalogued, but treat them as a lead rather than a citation. A forum post asserting a date is one person's recollection until you find the catalogue page behind it.

Sources