Identical construction, perfect balance, perfect match (2,000/2.000 & 2,000/2,000 on my Hickok 752A). One is labeled Valvo, the other Amperex.
They have gray oval plates, brown micanol bases and bottom D getters. I looked online and found an NOS pair for $700.00 and a used pair for $300. The boxes are pretty beat up. Valvo bottle printing looks very good but Amperex is fading. Note: these are an elegant replacement for the 6SN7GT but they cannot be used where the plate voltage is over 300V.