The C3m is a general purpose pentode with a 125 mA heater requirement for series heater chains. The construction is all glass with a built-in aluminium screening can.
The serial number Nr. 1820241.
The maker and Type on the top of the black painted screening can.
The C3m out of the screening can. Image courtesy of DiyAudio.
The wide glass tube envelope is 32 mm in diameter, and excluding the B8B base pins is 53 mm tall.
References: Data-sheet. Type C3m was first introduced in 1953. See also1953 adverts.
