Method

A mark is only as strong as its scope.

Every mark on a vintage razor is a witness with a reach. Some date the razor, some date a blade or a case, some only bound an era, and some turn out to have no key at all. Combining them under one rule is what keeps the answers honest.

One witness, one answer

A date code read against the printed year rows gives a year and a quarter, with the method named. A letter that carries no year at all is answered as a refusal.

Rule

One letter, several years

The date-code alphabet is twenty-five letters long and repeats every twenty-five years, so a bare letter yields two or three candidate years. The archive shows all of them and says which model feature settles the choice.

Rule

Agreeing witnesses tighten

A code on the razor and a pattern in the case that belong to the same era narrow the answer instead of competing.

Rule

A blade code is not a razor date

Blade codes date blades, and the collector source warns that blades in a set may not be original or may have been made before or after the razor. The archive labels a blade reading as a blade reading.

Rule

A patent date is a floor

A patent inscription says the razor cannot be older than the patent. It is reported as a lower bound and never as a year of manufacture.

Rule

A firm mark gives a period

A tang stamp, a registered mark, a workshop address and a country mark all produce periods or bounds. The archive gives the period and states that no year can be read from the stamp.

Rule

Disagreement is printed

Where the sources conflict — the start of razor date coding in 1950 against 1951, the letter Q, the end of the codes in 1988 against 2001, the Tech in 1938 against 1939, the two spans for one crown stamp — both readings are shown and neither is averaged away.

Rule

No key means no year

For Gillette Argentina and Brazil, for the Soviet razors, for Segal, for the Leicester prefixes, for the Canadian numbers and for the AutoStrop and Rolls body serials, the answer states the refusal and gives the era layer or the model window instead.

Rule

Not claimed

A year derived from a Canadian serial number: the source calls the Canadian data spotty and contradictory, and the archive refuses.
A year derived from a Leicester prefix: the meaning of E, F, G and H is not established, and the American table must not be substituted for it.
A year derived from an AutoStrop or a Rolls body serial: the numbers exist, and the key to them does not.
A single year picked out of the candidates for a bare date-code letter, without the model.
A patent date or a country mark presented as the year the razor was made, when each is a lower bound.
A mark registration year presented as a manufacture date.
A blade code, a wrapper or a case presented as the build year of the razor.

A Gillette date code D4 is the fourth quarter of 1958 — and, because the letter cycle repeats every 25 years, also the fourth quarter of 1983. The archive reports both years and calls the model in to decide between them. A tang stamp of “For Barbers Use” gives the working decades of a workshop, never the day a blade was ground.