This exhibit looks to be an RCA made valve that was sold by GM Parts.
The 6SR7 (Service code VT-233) is a double diode triode sharing a common cathode. The 'S' indicates that it is a single ended valve ie no top cap. The ratings are the same as the older 6R7 - with a top cap.
This triple sectioned valve was designed for superhet AM receivers. The first diode acts as signal detector feeding the audio signal via a volume control into the triode AF amplifier before the signal passes to the audio output valve. The second diode produces a DC voltage that is directly proportional to the audio signal and this voltage is used to control the gain of IF and RF stages of the receiver.
Compared to the pin compatible 6SQ7 this valve would exhibit lower gain in the triode stage.
The seller's branding.
As expected this valve was made in the USA.
The thin metal tube envelope is 25 mm in diameter and, excluding the IO base pins, is 51 mm tall.
References: Data-sheet, 1040 & 1043. Type 6SR7 was first introduced in 1940. See also1940 adverts.
