The VT-229 is the US Government code for the commercial 6SL7GT. The valve is a medium impedance double triode with high gain and superseded the 6SC7. It featured separate cathodes and was designed for use as AF voltage amplifiers, phase splitters and where required as a cascade amplifier of very high gain.
This valve was made by RCA but later sold by the retailer Bentley Acoustic Corporation. Here the rebranding has been limited to a paper sticker. For all glass valves with printed lettering the glass would be cleaned and their own lettering applied.
one triode section.
The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 60 mm tall.