It is a PLC. It is from the late 80's it was at one time the bestest little PLC on the market. They have a worth on Ebay because they are antique and any machines still running them would need an upgrade and new programming. Just show that it powers on in your ebay pics. This older unit did not have a normal connector for serial communications either if I recall. It had to be programmed with a hand held programmer too. I have one of those sitting somewhere too. Let us know what it brings if you think of it.