The tube at left is 1620 mis-numbered "1622". The 1620 is one of RCA's "1600 series" of of specially selected tubes, and this particular type is a 6J7 selected for low microphics. The tube at right is a "real" 1622. The 1622 is a 6L6 selected for low noise in theater sound systems. Most metal tubes have they type number stamped into the skirt. And, sure enough, the tube at left is stamped 6J7 and the one at right is stamped 6L6.