Northern Electric R221-D
DC Det/Amp Triode
~1926 (Canadian)

The R221-D was designed by WE for Northern Electric use and was similar to a UV201-A. The use of a metal shell at this time is somewhat unusual. The paper band was only used on the earlier production, later tubes had R215A etched in the glass. The WE version (hardly used) was made with an S bulb and bakelite base.