The 6SC7 is a metal enveloped double triode also marked with the American service code of VT-105. These double triodes have been used in guitar amplifiers and the ECC83 is used for upgrades although the 6SL7 was the first successor valve in the early 1940's.
We also have the 12SC7 that differs only in heater rating.
The Ken-Rad name is also on the cardboard box. The box also has the Bendix Corporation on it.
The IO base is 32 mm in diameter. The skirt is pinched to hold the plastic base in place.
The thin metal tube envelope is 25 mm in diameter, and excluding the IO base pins is 50 mm tall.
References: Datasheet, 1043, 3002 & 1040. Type 6SC7 was first introduced in 1938.