no clue really on GTSM, but if Reggie Bush is signing to that company exclusively for his autos, it has to be SOMEWHAT reputable right?
anyways, i know that GAI is reputable, but i really only trust it if the serial number starts with GP. GP = someone was present when the athlete signed. there is also GV which means that GAI verified the auto. personally, i only buy if its GP, but to each their own