Nor were there any S&W markings on our issue 1006 mags.
Never say never, we always say with S&W, but I will say that you are mistaken with this one. If not, and I am the one mistaken, it would be the FIRST evidence I’ve seen of a non-marked S&W 10mm magazine, and I’ve been playing with them since 1994.
To be fair to the discussion...
The marking that I’m certain you have missed is the “Smith & Wesson” visible on the very bottom of the floorplate, in the front half-moon cutout.
I have seen a faked floorplate with the cutout and no “Smith & Wesson” in it, but I’ve never seen it on a 10mm magazine.