Generally any pure solvent you use without wiping or scrubbing is just fine. Usually acetone, water and xylene are the solvents that can be used with impunity. Don't use fingernail polish remover! Let us see the clean version... BYW welcome to CT
My answer would be to send it in to one of the top TPG for conservation and then grading and encapsulation.
I really like the antique finish, to preserve it would start with some hot soapy water first to see if you can get results that way depending on what actually is on the coin may need something stronger.
Don't know if you guys can tell who are familiar with the coin, but is the indentation above the E supposed to be there or has the coin been damaged right there? Much appreciated for all of the informative responses.
Might just be the picture, usually has a raised area. Interesting enough, could the OP's coin have a chop mark? I almost see a slight circular depression there too. Would need picture with different angle. Good Eye. reading too much into it, probably just took a hit some time in it's Life.