It looks like a "D" that the post had broken off the die (that normally forms the center of the mint mark) and it is now starting a die chip under the mint mark.
It's probably a D. There is no MM for Philidelphia and there is an S MM for the proof coins. The proof coins have a different rim with a more squared-off appearance. So, it's a probably a D.
Disclaimer: While a tremendous amount of effort goes into ensuring the accuracy of the information contained in this site, Coin Community assumes no liability for errors. Copyright 2005 - 2026 Coin Community Family- all rights reserved worldwide. Use of any images or content on this website without prior written permission of Coin Community or the original lender is strictly prohibited. Contact Us | Advertise Here | Privacy Policy / Terms of Use