The mark that dates a razor is rarely the one on the outside of the lid. This is where the archived marks are found on the razors themselves, and what each one is evidence of.
On a Gillette, the date code sits in the top left and right corners on the underside of the razor guard, on both three-piece and one-piece models. On a three-piece razor the easiest read is to unscrew the handle and look at the baseplate directly.
Magnify and light from the side: a worn O reads as a Q, and a blurred 0 or 1 reads as an O or an I.
Serial numbers sit on top of the guard, or inside the barrel of the handle. On British razors the dating tables often record the exact place of the stamp — guard plate top, outer barrel, inner barrel — which is itself an era clue.
From 1907 the letter comes before the number; with the New Improved from 1921 it comes after it.
The tang is the flat surface between the blade and the pivot, between the edge and the erl. Firm names, mottos, trademarks and the country stamp are struck there, usually on both sides.
Repolishing destroys the stamp irreversibly — photograph both sides of the tang before anything touches the blade.
ENGLAND, GERMANY, FRANCE, SWEDEN or U.S.A. on the tang next to the firm name; on a Gillette the single letters V, W, Y and Z as plant marks for Spain, France, England and Canada.
A country mark is a lower bound from 1 March 1891, never a year, and a plant letter is never a year letter.
Blade date codes are printed on one side of the blade or on the cartridge. On a Rolls Razor the two-digit year is struck on the end of the blade spine, next to the word razor.
A blade code dates the blade; a Rolls blade with no year is a replacement and gives no date at all.
The wrapper, the dispenser and the box carry their own eras: the first date-coded blades in 1930, the blue dispenser around 1950.
A number on a wrapper may be a steel lot number rather than a date.
The case, the shape of the box, the material, the inscriptions on the lid, and the instruction sheets or price list inside it.
The case dates the set, not the razor — and a Rolls case carries no year, only its model line.
Struck or etched on the razor: the Christy massage bar patent, the Gem and Ever-Ready patent wording, early patent dates on a safety razor.
A patent date is a floor. The razor is no earlier than the patent and may be much later.
On a safety razor: open comb against safety bar, the end caps from 1946, the notch in the guard, the slots in the plate, the tip colour, the dial.
Features place a razor in a model family, and the family carries the years.
On a straight razor: the grind of the blade, the thickness of the spine, and the material of the scales.
This layer cuts off an era rather than dating a razor: wedge is early, quarter hollow is transitional, full hollow is from about 1880.