I got an an ABC Shell razor in the mail today and it has two codes. One is the regular date code and the other is prefixed with an "L" denoting that it was sent in for repair. This "L" prefixed number got me wondering about marks that Gillette used for razors that were returned for repair. Other than the "L" prefixed number, I've read that the imprint of a "G" inside of a "D" also denotes a razor returned for repair. Are there other markings used for such purposes? Or are these the only two that are known? And I would assume that there is no way to tell, but is there any way of dating these two marks? Were the two marks used at the same time (perhaps different repair work or different repair centers?) or was there a year in which they transitioned from one to the other?