Too late now but in the future when purchasing a firearm the salesman should allow you to inspect the firearm before filling out ( or somewhere in there) the 4473. If you see a defect you can ask for him/her to pull out another to inspect...If they don't like that, walk....
In this day & age I'm quite certain all the working internals are MIM, doesn't mean it's a bad thing but it answers the question. I'm sure the pit is cosmetic but let me ask, is the pit on the surface of the hammer that strikes the primer/rides under the slide? if so then I wouldn't worry about it as it will most likely wear within a couple hundred rounds unless it's a deep pit. If it bothers you enough call Remington and they can replace the hammer or if you want to do it yourself (it's not hard at all) there's tones of aftermarket parts out there. Pick your poison... :rock: