2430 in not the serial number of the gun but rather the official proof number, or Beschussprotokolnummer of the Ferlach proof facility (Beschussamt). So there is no way the 24 indicates the maker in this case.
15182 is the factory serial number of the gun which corresponds to the largest Ferlach gummaker, Franz Sodia. Some F. Sodia guns from my notes:
number 3325 from 1952 (unsigned),
number c.10000 from 1960,
number 23164 from 1980.
I'm quite sure that the drilling in question is an unsigned Franz Sodia piece from 1967.
Cheers,
Jani
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