Here is an original condition Ron Coelho (RPC) tenor mouthpiece with the red lettering. This piece is engraved .110" and measures .115" on my gauge.
Ron Coelho was a prominent artisan specializing in saxophone mouthpiece who passed away only a few years ago. He worked with many professional players, even making the mouthpiece used by Jimmy Heath until his death.
This piece features a tight core and a long, flat-ish baffle and speaks very quickly and powerfully. Red Letter pieces are sought after for their work and the cool streamlined body shape.