If this is accurate: http://www.pc-history.org/sol.htm then it does look like the SOL-20 might have been sold complete before 1977.
Can you point to evidence of that? Everything that I've ever read/known about the SOL-20 was that it didn't actually hit the market in pre-assembled or kit form until 1977.
This quote:and this one:
The SOL was the first personal computer to only be sold as a factory-built computer.
By 1977, SOL was the dominant personal computer in the industry and was the principal product in my store.
Make it sound like he was selling complete units in 1976..
Interesting, but as you say, I'm not sure how accurate it is. For instance, the line "...was the first personal computer to only be sold as a factory-built computer" is most certainly not accurate, because it was positively available in kit form (which is not a knock--even the Apple II was available alternatively as a kit (though not the PET or TRS-80)). Also, the perspective seems a bit skewed, as maybe the SOL was HIS store's best selling computer, but I don't know of any evidence it was the best selling computer anywhere else for any particular period of time. It's my understanding based on the most reliable sales figures, that ironically (because it has historically been the most mocked) the TRS-80 was the best selling computer (mostly due to the ubiquity of Radio Shack stores) into the very early 1980's.
I'll check my own stacks to see if I uncover anything. I'll definitely believe 1977 for complete SOL-20's, but I'm still not convinced it would have been before, and then I guess WHEN in 1977 would have been important as well.