I do have the answer to your question, Quintus. There are technically four but five different Mint Marks: Berlin, Mint Mark A, Munich, Mint Mark D, Stuttgart and Karlsruhe merged in 1998, so they're actually a single mint now, but they mint coins with both Mint Marks, which are F for Stuttgart and G for Karlsruhe, and Hamburg, Mint Mark J. The fun (or infuriating) thing about collecting West and United German proof sets is that all four mints produce a proof set every year and the merged Stuttgart-Karlsruhe Mint issues two, one for each Mint Mark. So, to have a full set, you need four or five sets a year, depending on the year.