It is a replica of the Ohio Scientific Superboard II. The original SuperBoard II was one of the first affordable computers that featured a full keyboard, video output, BASIC in ROM.
At a price of $279 in 1979, it was an amazing bargain at the time when compared to systems like the Apple II that retailed for about $1300. For that you got an assembled board but needed to add a 5 volt power supply, monitor or TV set and RF modulator, and cassette tape for storage.
I owned one that I purchased in 1979 and it was my first computer. With it, I learned BASIC and 6502 machine language programming.
The SuperBoard /// is Vince Briel's replica of the original SuperBoard. It features a 6502 processor, but simplifies the design by replacing a lot of logic chips with a Propeller CPU. It is software compatible with the original system.
It is sold assembled or as a kit. I opted for the kit.
To date I've made three YoutYube videos on the kit, covering unboxing, assembly, and basic operation. They can be found on my YouTube channel.
I also have some files on my github account including a handy Quick reference, the OSI firmware including BASIC, and a port of my JMON monitor program. The Visual Monitor program that I entered a few months ago also works.
Below are some useful web links.