Processor Technology was started as an add-in card company producing mainly memory cards for the MITS Altair 8800. Like many similar companies, they quickly expanded into producing competing systems themselves.
The SOL-20, designed by Lee Felsenstein and conceptualized by Bob Marsh and Les Solomon, was a seminal personal computer that was first to include integrated keyboard, video and ROM in the same package. This model quickly became the industry standard for user friendly personal computers.
The Sol-20 was an 8080 based system that incorporated the Processor Technology VDM-1 to produce video on a television or composite monitor. The system included a monitor ROM that allowed the user to boot the machine into a semi-usable mode on power up.
The machine in my collection is in exceptionally good condition and works perfectly.
The SOL-20 had a very clean design with a large motherboard, a five slot S-100 card cage and a relatively small power supply.
From the back you can get a clear shot of the card cage and the "personality module" on the bottom right.
The SOL-20 runs perfectly and a quick memory dump can be seen here on a standard composite monitor hooked up to the system.
I've got a manual around here somewhere. As soon as I dig it up I'll post pictures.