This is the Mec-Gar 19 round 9mm magazine for Tanfoglio Witness Small Frame pistols.
Mec-Gar are the industry leader in pistol magazine production, providing OEM manufacturing for many big names including CZ, Beretta and Browning.
Frame Size
Tanfoglio have two frame sizes. You can ID them from the magazine width.
This is the Small Frame size - magazines are approx 20.1mm wide at the rear of the magazine.