Some of the boxes are weathered and have not stood the test of time. But the 300B by Western Electric remains to be a timeless classic. With good linearity, and long life.
These boxes were stashed away in a vast collection, donated by Silk Electronics, a former vacuum tube dealer in Salt Lake, UT.
This coveted tube seems like a great place to start, as I sort through the collection. Supporting my local HAM Radio Clubs "UARC, SLCARC", and the Silk family.
3 are in original boxes, and 3 have been tested, and reboxed.