10 dollar 1900 S - small letter?

Hello

I have received a image of a 10 dollar 1900 S coin with a small difference on one the sides.  The design is the same but on this ten dollar coin the letter of the mint mark looks smaller than other examples from the 1900 issue .  How could this difference be explained? The seller told me that the weight of the coin is 16,71 gr., diameter 27 mm and that it has thickness of 2 mm.

Any help would be much appreciated. 

Mint marks were not on the dies when engraved from the master die. They were put on by hand with an S punch and hammer. That explains why location and depth can change slightly from die to die. Here are two PCGS certified $10 coins:

If there are no other indications of a counterfeit, I would not be too concerned about the mint mark.

I don't like this coin at all and believe it to be counterfeit. It is “off” in so many ways and the odd color was my first concern. Forget about the mintmark for now and just compare some of the text detail near the mint mark. First look at the N in ten and then the D. Not right. Now even the orientation of the mintmark. Between the E and N on the 2 genuine, and essentially only over the N in the photo you provided. That's just a start. Be careful here. Photo you provided.  -  PCGS  -  NGC                                                               

rsirian1 ,harryg thank you both for the information that you have given.  I didn't know that the mint mark wasn't part of the original die it self. Probably that's why there is a small difference in the size of the letter. 

Couldn't the “form” for punching of the letter of the mint mark was worn-out in time?

The weight and other parameters are looks to be normal ,but the second post of harryg guides me in other direction and now I'm startin to think whether the coin is authentic or not. The N and D does look a bit little strange in shape and more thinner when compared with the NGS images.