I have three of the early TAPCO standard pistons (2 groove) and they have the TAPCO USA somehow burned (etched) into the metal. The lettering was black but now after use the black is gone but the lettering is still there.
I like the way they did the new pistons with the relief cut. Oh, why did they change from the 2 groove to 3 groove? Was there a problem in functioning? I haven't had any problem with the ones I have.