Glock does put anti seize on the rails of their pistols. The anti-sieze is more for protecting things during storage and shipping of new pistols. I have seen it debated to death on whether you should leave the anti seize on the rails or remove it before shooting the pistol for the first time. I personally leave the anti seize in place and clean/lube everything else that needs it before shooting a Glock for the first time. I usually only shoot 100 rounds on the first range trip to test before doing a good cleaning of the pistol and then shooting some more for final break-in and testing. Other people's methods might differ from mine.