Normally, I just exchange these coins, but this one stuck out, so I kept it. The reverse photo didn’t come out as well as hoped, so I took another one through the 2x2.
That 1988 seems to be in very good shape. Certainly worth keeping. Collecting the early issues of the BRD is fun - there are scarce dates and mints for all of the issues, 1 Pfennig to 5 Mark. Consulting my catalogue, the scarce 10 Pfennig to watch out for is the 1967 G (Karlsruhe). The 1 Deutsche Mark pieces is also quite interesting. A number of scarce issues also there, like 1954 G, 1955 G, and 1968 J. I used to collect them out of circulation before the euro took over, and was able to find all of the scarce years juts by going through my pocket change.
I used to dig through them looking for the years, but realized it didn't interest me. I probably sent in a couple of the "rare" ones. I think I did find one or two of the 1 Marks you mentioned. I'll see if I can find them.
