The E1796 is an M-OV experimental valve but the envelope also carries the Type KT101. So this could be a KT101 or it could be a variant - we have no way of knowing.
KT101 is an audio output beam tetrode. With a load of 3,000 Ω and a cathode resistor of 180 Ω the KT101 would generate 3.8 W at 12% distortion. The KT101 is also specified for use strapped as a triode.
The serial number is 90 and the heater rating seems to be in the same hand and matches the KT101 that someone has added to the label.
The KT101 as would be added during main production.
The wide glass tube envelope is 32 mm in diameter, and excluding the B8B base pins is 70 mm tall.
