Why do some of the graded (pcgs) 1955 DDO coins only say Double obverse and some say ddo f-101,fs-021.8 Is there a difference invalue of the same grade?
Coins are made from different dies so the numbers identify which ones. There can be multiple errors in the same year so 101, 102 etc. Identical coins will be the same number.
I think what you are asking is about the extra info, You have to pay most TPG companies to add the extra info where they are certifying that it is that particular die, rather than another 1955 DDO FS-101 is worth 10X more than a 1955 DDO FS-102. The older Fivaz-Stanton codes were the decimal types 021.8 and 021.9, newer code are FS-01-1955-101 and FS-01-1955-102.