ive seen a few things about this penny. Is it really worth something? If so, how do I tell for sure mine is?
No mint mark means it was minted in Philadelphia. The only year they had the "P" mint mark on a Lincoln Cent I believe is 2017. I see PMD (post mint damage) and maybe a few plating blisters. Check this site out to learn more about errors: http://www.error-ref.com/
The 1990 No S Lincoln worth a huge premium is the Proof example. All proofs from that year were suppose to have the S mintmark. Somehow a few were minted without the S even though they were made by the San Francisco mint. Your Lincoln is a business strike intended for circulation and was minted in Philadelphia. A proof would have mirrored fields.