From the Heathkit Virtual Museum:
During the Heathkit era, which lasted from the late 1940's through the mid 1980's, building Heathkits was a favorite activity for many electronics enthusiasts whose interests ranged from hi-fi/stereo and ham radio to computers, radio control, and home electronics.
As the cost of electronic assembly fell to zero and consumer interest in technology increasingly did not extend beyond software, Heathkit no longer found a market for their TT-1 Mutual Conductance Tube Testers and closed their doors. Beyond learning about electronics at an academic level, assembling a Heathkit project provided an unparalleled experience to learn the engineering of consumer products.
I believe that the W-6M tube amplifier would find a ready market if it were sexed up a smidgen.
Heathkit Virtual Museum