I was wondering if someone could help me place this plate as North American or European by the makers stamp. It appears to be brass, handmade(assymetrical), and my guess would be 18th century. I'm not really sure what this adorned either with the two openings, only one of which is keyhole shaped. It appears to be stamped TT on the back in two places. Does anyone know of a reference for hardware maker stamps? Thanks for any input.