A rather nice example of it's genre; an honest piece.
This piece has had the best part of 200 years to acquire the patina that it has.
Patina wise, compare with contemporary British copper coins.
I guess that if it has been cleaned, it must have been done with a rag and hard rubbing. That would make it quite difficult to distinguish between wear and cleaning.
I don't think it has been cleaned, and has only experienced some light circulation wear.
Nevertheless, cream metal polishes have been around for a long time; that would give credance to the idea of how the iridescent toning may have been acquired.