Acorn System-1 - 1979
This was similar to the Sinclair Mk14 in design having a 7 character LED display, hex keyboard (the numbers 0-9 plus the letters a,b,c,d,e,f) but had a bit less memory (100 bytes) and you could load and save programs to cassette. The big difference though was that it was Eurocard compatible, this meant it could connect to other cards. With these, the System 1 could be expanded to 800 bytes, BASIC added as well as a proper video output.
This is another computer I am still on the lookout for.