Aftermarket, likely...
True factory mags are quite distinctly marked with "stitching" or "ladderback" seams and SIG markings as to caliber.
If you're lucky, you'll find a Mec-Gar mag with equal or greater than standard capacity...id est, 15-17 rounds.
That said, try your "CC" mag...it may work just fine; but I would not trust if for everyday carry.
