This is the Mec-Gar 11 round .45 ACP magazine for Tanfoglio Witness Large Frame pistols.
Will also fit the CZ 97 with minor adjustment, on which the Tanfoglio was based. The CZ 97 and magazines have been discontinued.
Mec-Gar are the industry leader in pistol magazine production, providing OEM manufacturing for many big names including CZ, Beretta and Browning.