This is an IBM 1800 supplemental control panel I picked up on Ebay a few weeks ago. The service tag is 1969. It's full of SLT chips. My theory is that it may have been used to monitor data transfers or to make sure one machine was cabled up correctly to another, I don't really know. There were computer-like devices that used the CPU of the mainframe computer to test and manipulate the mainframe's data as an add-on function for diagnostics and repair purposes. This type of device contributed to the evolution of stand-alone microcomputers, the Altair was not simply a simplified PDP 8. Add a microprocessor and RAM to a device like this and you have a microcomputer.
I cleared out the foam that lined the rear inside cover, it was disintegrating and eventually would have ruined the unit. I tried to find a way to cover it up, but it was too far gone. I have to clean all of that sticky dust off the components. You'll notice in some of the hi-res shots that there are little brown dots, that's the foam.