I have a 6 in, 6 out Entertron Smart-Pak PLC. Only the ins, outs and the scan LED are labeled. The other two connectors, I assume are for power and RS-232, not labeled. The only other markings on the board are ENTERTRON SMART-PAK and hand written in sharpie on the bottom 10/92-188. There's a typed and hand cut paper label on the firmware chip SMART-PAK Ver 3.24

That is it, that is all. Doesn't even have the component locations numbered like a properly made PCB should.

I sent an e-mail to Entertron days ago, no response. They have nothing on their website for any of their products this old. It does NOT have the 0.1" expansion header and the screw terminals are blue, not unpluggable. Their later stuff has the green, unpluggable terminal blocks.