KurtO,
Guns without "maker's marks" were typically made by a known manufacturer "for the trade" to be marketed by some other dealer who may or may not add their own markings to the gun. The "AK" is the touchmark of someone that did some work on the gun. There is no ledger or listing of these names showing positive identification. There are others that may make a guess (S) of names that can fit the initials.
Mike