I have 1943 D Merc Dime. I was looking at the mint mark and something just seems off about it. The D on the '43 dime looks odd to me because the D is "straight", in pictures of most other D dimes that I have seen the D's seem to be tilted a bit in the same direction as the E in the word "One"? Also the dime is very "clean", except for some black build up around the D mark. Has anyone seen this before?