Who was CM? Farmer? Just a parishioner? An unknown central midfielder? Probably not in 1812.
He, or she, didn't warrant much in the way of a slab of slate for their memorial and the whole thing looks a bit haphazard, even the incised lettering looks as if the workshop apprentice cut it while practising.
You can almost hear, 'you're in luck sir, we've got one here with the right initials. We'll just add the date and there you are.' Followed by the deal clincher, 'it's cheap too.'
We'll never know.