[jimmy james]

May be from S&W. Nice mag. Works well. 7rnd w/witness holes. Just says 45 ACP near bottom.

 

[SparkyAZ]

My guess is Springfield Armory and I think Checkmate makes these mags...??

 

[Snooze]

The sidewalls, witness holes, .45 ACP marking, and (non anti-tilt) follower all look like the 7-round magazine that came with the Springfield Armory Defender Series Mil Spec I bought recently.
Only difference is yours has a base pad rather than a steel floor plate.