The 6SC7 is a metal enveloped double triode. 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.

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.

 
Pin Connections

IO	1	2	3	4	5	6	7	8
	m	a(2)	g1(2)	g1(1)	a(1)	k	h	h

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	ra	gm
	6.3	0.3	250	-2	2.0	53,000	1.325

Thanks to Frank Philipse for supplying the above PDF datasheet