Beautiful 1944 NOS matching pair of rare, special application grade, low noise SYLVANIA grey glass VT-231. These are unused stock from a collection of industrial grade electronics I recently acquired. These were special RF shielded and were selected out of many VT-231's for low noise and close triode matching.
They also have matching 1944 date/SC-966-A plant codes on base. They come in old white military boxes they were re-boxed in after testing.
They have been listening tested in a high resolution system and sound excellent!
About as nice a pair of these as you will find anywhere.
Fully tested on a calibrated Hickok 539C at 2800/2900 & 2950/3000 where min is 1640 & NOS 2550.
Please see my other items for more top quality tubes from this collection