(!!!) 31 RCA Radiotron Balloon NOS 1920's (13.2ma)
(!!) (#1 31 Pair) 31 National Union engraved base NOS 1930's (13.8ma and 14.2ma)
(!!) (#2 31 PAIR) 31 Tungsol and RCA Victor NOS same build 1940-1947 (12.8ma and 13.0ma)
(!!) (#3 31 PAIR) 31 GE and Coronado same build different shape top mica 1940's (15.0ma and 15.6ma) (Highest Ma)
(!!) (#3 31 Pair) 31 Philco and RCA engraved base different top mica NOS 1930's (13.4ma and 14.2ma)
(!!) (#4 31 PAIR) 31 Westinghouse and Sylvania NOS same build 1940's (12.0ma and 12.8ma)
31 Coronado by Sylvania engraved base used/good 1930's (11.5ma Gm=700)
