I'm a little confused, I bought an unopened 1976 mint set, BUT the envelope says 1975, why would that be ?
If the envelope says 1975 then it's a 1975 set and only the Quarter half and dollar will be dated 1976, the rest of the coins will be 1975's. And the Ikes will most likely be type 1's. If it was a 76 set all the coins will be dated 1976 and the Ikes will be type 2's.