SOMETIME IN THE 20'S. I READ AN ARTICLE A LONG TIME BACK, MAYBE IN AN OLD "PICKIN" MAGAZINE, ABOUT A TENOR PLAYER, MAYBE EMANUAL SAYLES(?) WHO HELD A WOODEN CHAIR SEAT IN HIS LAP AGAINST THE BACK OF HIS BANJO. CHECK WITH GIBSON BANJOS BECAUSE THAT COMPANY HAS BEEN THROUGH ALL THE VARIOUS ITERATIONS. TRAP DOOR RESONATORS I BELIEVE EXISTED PRIOR TO WHAT WE USE NOW.