Just bought box of odds and ends at sale. I'm a wheel gun man.
Got 2 9mm double stack mags, 14rds. Fits, black plastic followers, stainless body, mag. catch & 2 witness holes, and S
on right side. Left side 1 hole, bottom plate has S&W logo and detent to strip. Can't find picture of factory mag. to compair.
Any info appreciated, Megar5900 series looked similar.

Early 5906 mag. I have one exactly as you describe. Can be updated to a 15 rnd mag with and orange follower.