Impossible to be a RPM. The mint marks were on the dies design since 1990. Looks more like die deteriation on the mint mark. If you look at other devices on the coin you should also se more deteriation on the devices facing the rim. Keeping in mind the composition of the nickel, the nickel in the planchet makes the dies wear faster. Thus you see this more often on nickels.
That is a very interesting mint mark though is it not? It looks almost like a tilted S under the D that almost looks like a D over D as well but it would have to be some sort of damage as coop has pointed out since it is 1990 and later.
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