Yep, the first in a line of reasonably successful machines, the System 1 was a single board computer (SBC) built round the 6502 processor. Originally available as a kit, it came in 2 parts, both standard "Eurocard" sized, the CPU module itself and a keyboard/display/cassette interface module that sat on top of the CPU board. This kit I've got only has the CPU module, but I had to have it since it's unbuilt :) Later machines in the range were simply numbered 2 to 5, steadily increasing in power and expandability. One interesting note is that the System 2 had an external keyboard, and an optional case for said keyboard became the case for the Atom.