16 Round 9MM Mag for Smith 59?

[Drakejake]

I bought two mags on e-bay. They were billed as mags for Smith and Wesson 59's. I got them for use in my Kel Tec P-11. I was surprised to find that they easily held 16 rounds instead of the expected 15. They are blued, have two holes on the right side, one hole on the left, a flat metal base plate inscribed "SW, 9MM, A." There is a visible weld seam on the back. Someone has told me these were not made by SW. They are not Mec Gars. They work too well to be Pro Mag. Can anyone tell me what company made these mags?

Thanks,

Drakejake