The GB stands for 'Gasse Bremske' (CZeck me on the spelling), or 'gas brake' referring to the method of recoil management. I have seen a couple of the pistols at gun shows (18 round magazine, OH YEAH!!!), then realized that the mags were made of unobtainium, and priced north of nonaffordium. My interest died quickly, when compared to my recreation fund. I shoot CZs now.