This is tricky - I have gotten some relatively rare items on Audiogon (Symphonic Line Kraft 250 mono amplifiers, Accuphase PS-500 regenerator / conditioner, Stahl-Tek Vekian Opus DAC, Tidal Contriva Diacera SE speakers) but I cruise the audio ads somewhat frequently, so its hard to say I have never seen another (although I would be comfortable saying no more than a couple).
However, here are several "sole" examples I can think of:
Silver Rock Phono preamplifier (was Stereo Times review unit)
EASE / Counterpoint Magnum Opus phono premplifier (a Counterpoint SA-9 with upgraded parts and cosmetics - only a handful ever made)
Silver Rock TVC with two switchable inputs (almost all of them are one input)
Promitheus Signature TVC (with two chassis and copper plates - still kicking myself for selling it)
Following up on the above posts, am a fan of MFA as well - Scott Frankland (the "F" in MFA) is a stand up guy.
However, here are several "sole" examples I can think of:
Silver Rock Phono preamplifier (was Stereo Times review unit)
EASE / Counterpoint Magnum Opus phono premplifier (a Counterpoint SA-9 with upgraded parts and cosmetics - only a handful ever made)
Silver Rock TVC with two switchable inputs (almost all of them are one input)
Promitheus Signature TVC (with two chassis and copper plates - still kicking myself for selling it)
Following up on the above posts, am a fan of MFA as well - Scott Frankland (the "F" in MFA) is a stand up guy.