This is an Atari STFM, has TOS a ported version of the popular GEM OS on ROM and is very nice to use.
Here the mainboard can be seen, with the wires for a very homebrew looking memory add on.
This shows the memory add on wires in detail and the methods used to increase memory on these machines.
The complete computer can be seen here with the memory modules seated in the middle and floppy drive to the right.
From left to right the ports are serial parallel monitor and power.