I found this little jem. As most know the s mint mark was not struck in 1985. Why and how much? Thank you.
Not sure where you got your information from, but "S" cents were minted in San Francisco. You have a proof strike cent. There were approximately 3.3 million proof cents minted in San Fran that year. Your coin is neither, rare, nor valuable. I wouldn't pay more than a few cents for your coin depending on if the scratches are on the case or the coin itself. That being said, it is a fun find. Where did you find it?
Often referred to as an "impaired" proof since it is outside of its protection and shows signs of wear.
From ngccoin.com....ms63/$3.30, ms64/$5.50 and ms65/$7.00. As posted earlier in this thread by Dunk 2, ms63s are selling for $1.99, and it looks like a better grade ms66 sold for $19.95. To put your coin in perspective for you, if you found it unprotected in your change and it has evidence of wear, it is an impaired proof that cannot now grade higher than au58+. The wear sustained now outside of its protective holder means its condition is less than "mint state". The sad result is you may only be able to sell it for .50 cents to a dollar, and you should not expect to sell it for more than that. I suspect someones relative passed away and heirs used proof set coins to pay for something. This injected them into circulation and permanently damaged their proof surfaces. This illustrates gross ignorance by the heirs and IMHO, is one of the most harmful things that can happen to a coin, short of using one for target practice...Spark Note: edited to fix faulty grammar, much thanks to @NOS