One of the SC-102's I have still has the tubes in it. I'll have to dig it out of storage and see what's written on them as far as who-dunit. It's a 6 Volt Compactron which looks just like a 6JS6, they are mounted on their sides one on top of the other. I can't recall whether 6JS6's are rated to do that. The industrial number may just be a tube rated for mobile service with a rugged filament. This is why I was asking if anybody had the specs for the tube, so that I could do some engineering to replace it with something more common.
I am starting to like the idea of changing the sockets to ceramic octal and using a pair of 6883's (12 volt 6146) because they are so cheap, although using 6JS6 class tubes means the sockets could stay as they are.
If it's a 12 volt, take a peek at the 8950. It's a 12 volt 'version' of the 6KD6 / 6LF6 / 6HF5. Used a lot in the '10 meter' amplifiers, and some multiband amps and SillyTronix used them in their Drifttronix 1011.
The 8908, if you can find one, is a great tube, but more of a TX tube than a compactron.
The M2057 is a ruggedized 8950. The M2057 and 8950 both run 12 volt fils. BOTH the M2057 AND the 8950 where run in a plethora of amplifiers in the horizontal position... I ran a PAL 350MDX, it had the original tubes marked PAL in the late 80s when I acquired it, 4 total, horizontally polarized
. The 6LF6 was also run horizontal by Palomar and I seem to recall one other mfg doing it.
Their are a LOT of .ru tubes adaptable. I'm sure you can find SOMETHING in the junkbox, but the 8950 is a DAMN fine tube, as is the 6KD6 series.
--Shane