Factory Beretta (P.B.-marked or M.D.S-marked. regardless of American or Italian-manufacture) 15rd magazines will have the right-hand-side cut-out for the earlier "92S" models. This includes millions of Factory magazines made since the late 1970's.
Factory Beretta USGI M9 (regardless of American or Italian-made) 15rd magazines WILL NOT have the right-hand-side cut-out for the "92S" models. These are the early and late USGI Factory 15rd M9 mags made by either P. Beretta or Mec-Gar (under contract). These have the USGI Cage-code and part-number roll-marked on the right-hand side of the magazine-body.
Most Italian-made commercial and/or police or contract Mec-Gar 15rd and 17rd magazines will (usually*) have the right-hand-side cut-out for the earlier "92S". Mec-Gar made 15rd/17rd mags for decades with a cut-out for the "92S". The newer Mec-Gar "M9" 18rd and new, redesigned 15rd (made from the 18rd mag-body) WILL NOT have the cut-out for the "92S".
No Checkmate or Airtronic-contracted USGI 15rd mags will have the cut-out for the "92S".
Sorry for the long post. Hope this helps.