Was given the opportunity to search a mansion property dating earlier than 1900. Spent about two hours there and found this semi key wheat from 1911. Has an S.
The following are some pics old and recent of the house.
It is already a "details" grade coin since it was pulled out of the ground. Resist the temptation to scrub it after soaking. You definitely don't want to put scratches on it.
Personally I start off with about a 30 minute soak in regular hydrogen peroxide. Then keep changing it out as the coin gets better. After soaking and patting dry there is product called "Verdi-care" that was specifically formulated for copper coins. A drop or two of Verdi-care is all it takes. (I've heard it is hard to find lately, even on Ebay.)