Gillette Date Codes were used from January 1951 until 2001.
They are found in the top left and right corners on the underside of razor guards, both 3 peice and 1 piece models.
The letter represents the year, found on the chart below, and the number 1-4 correspond with the quarter of the year.
Waits, and "The Complete Gillette Collector's Handbook" and Collector's Guide to American Razor Blades" by Phillip L.
Dating Gillette Razors and Blades: "How old is this razor? Sometimes patent dates are a help, but they give you the front end of the date scale, and not always too exactly.
Some razor makers put serial numbers on their razors, but we don't always have the key to how the serial numbers fit to dates of manufacture.
Razor Serial Numbers were impressed on all Gillette razors from 1904 until 1921, and on deluxe models from 1921 until 1931 (except for a period in 1927-28).
This corresponds to the time King Gillette was directly associated with the business, and may have been at his insistence.
These serial numbers were on the top of the guard, or sometimes the inner barrel.
There were no razor serial numbers from 1931 until 1951.
The blade system adopted in 1931 is still in use today, and was used on razors as well after 1950. Other makers included serial or manufacturing codes, but we do not have the keys.
Auto Strop and Rolls are two well known manufacturers who serial numbered their razors.