You would think there wasn't chess clubs all over the world where you can walk in and find people who know something about chess and copy their game. Just copy a game two ~1700s play in a friendly match and have your characters play that exact game - you will have your choice of games so you can choose who wins. Get the best player in the club to advise you if you want the characters to talk about something - it isn't hard to get this right with a little expert help.