When Cary first built the 1610 amplifier they used the WE 308B. They were having trouble getting those WE tubes (only used in the Beach Master amplifier in WW2) so KR made this copy and called it the KR 1610.I sold a pair of WE 308B's to Koji at EIFL a year ago. The tube is not that different than the WE 212.
Tre'