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.

How often should you change your razor?

Ideally, you want to change your razor blade after 5-10 shaves. Gillette actually recommends 5-7 shaves, but this is just a general rule and it actually comes down more to the thickness and density of your facial hair.