The receiver or the barrel is marked? Barrels are routinely marked SB2, receivers have never been marked. The SB1 receivers should be marked with similar info to that on the website and in the catalog....*Note: The frame of the 44 Mag. (SB1-S44) and the 357 Mag. (SB1-S35) cannot be fit with any other centerfire rifle barrel. They are capable of being fit with accessory shotgun barrels, but their rifle capability is limited to the specific 44 or 357 Mag. barrel that it is shipped on the gun.
I've shot the 225gr FTX LE ammo in mine, it shoots good, the comp bullet just became available, so I wouldn't expect too many have tried it yet. The 265gr bullet is a .444 bullet, likely too hard for the 44mag.
Tim