Leupold started using an alpha/letter in the serial number in 1974.
Leupold scopes made between 1974 and 1992 had alpha/letter prefix E thru Z, not including I, O, and Q.
Leupold scopes made between 1993 and 2012 had alpha/letter suffix A thru W, not including I, O, and Q.
My older, pre-1974, Leupold scopes have taken on a "plum/purple" tint.
According to Leupold, FAQ #3 under "resources", the Vari-X series of scopes are comparable to the currentl Rifleman series.
Jeff