Silver Anniversary Set Question(S)

In the ASE anniversary set I received, the regular proof and the UNC in the silver set have "W" (West Point) mint mark; the reverse proof has "P" (Philadelphia). All my regular proof eagles (those not in the anniversary set) have "W", although I don't think this has always been the case on the proofs. All my regular UNC eagles are without mint mark, but I don't have very many of those either. When I received my ASE anniversary set, the UNC coin has a rather large mark in the main focal area of the obverse (the field behind Liberty). I thought I could replace it with a regular UNC silver eagle, but I need to get one with the "W" mint mark, and in one of those capsules that house the coins in the set. Is the "W" mint mark on the anniversary set UNC's special to the set, or are there other "W" mint unc silver eagles? Will the mint replace the coin?

Of course, my question wouldn't be relevant to Anniversary set coins that are graded by TPG's. I like the black box and capsules that the coins originally came in and, until I intend to sell it, I don't see the point of sending it to be graded. I don't know much about American Eagles because I don't have very many.

Thanks for any advice.