I just picked up a FDE GEN4 19. Put about 1000 rounds of various ammo through it without a problem other than a few weak ejections. I always try to buy a backup RSA to have on hand in case it's needed. So the one I bought from Brownells has the numbers 0 1 3 on the bottom of it and the one that came with the gun has the numbers 0 3 4 on the bottom of it. Can anyone tell we the difference between these two RSAs?