Hi Bwhite,
You've arrived at the erroneous conclusion that base prints mean something. They don't. It was not uncommon for base prints to be labelled months after the actual date of production, sometimes completely removed from the actual site of production (e.g. at distribution centers, where a lot of rebranding occurred). With the two notable exceptions of 5692 and W/WGT-suffixed tubes, there was no such thing as as a military-designed 6SN7 .... only different base prints for military-designATED 6SN7 (the US military used VT-231 as its numbering system, the British used CV1988, etc.). Yes, these tubes had to be made to milspec standards, but no, they weren't any different then their commercial-bound counterparts. There wasn't a factory churning out just military-designated tubes. Factories distributed the same exact tubes with different prints based on its intended destination. A Tung Sol 6SN7GT in commercial red and blue boxes is the exact same tube as a Tung Sol VT-231 in tan military boxes.
What are the three "flavors" of Ken Rad black glass you speak of? I've removed the glass from about half a dozen Ken Rads with various base prints (fwiw: I'd be happy to post pics of the internal constructions of some 6SN7s). Perhaps you've stumbled across some insight I overlooked. The only differences I've found is minor mica variations and grid posts constructed of different materials.
It's logical fallacy to assume that the differences you hear in tubes is due to vintage or material differences. Each and every 40s tube was hand-assembled by both skilled and not-so-skilled laymen. Thus, they're subject to variations due to build quality alone. Chances are, any differneces you heard were quality control related more then anything else.
To clarify, I am not doubting you hear differences. Some people simply have better auditory acuity. But you are the first person I know who can hear marked differences in Ken Rad black glass 6SN7/VT-231.
I currently use a Chardonnay.
