An Altair 680 that I  picked up a couple years ago at a hamfest.  It was part of a large collection of stuff that was donated to the radio club from a former amateur radio club member's estate.  It predates my first encounters with computers by a few years, but not too many.

From what I've read, the Altair 680 is a smaller version of the Altair 8800 and powered by a Motorola 6800 microprocessor, while the 8800 used an Intel 8080 microprocessor.  The 680 doesn't seem to have been as popular as the 8800, and there isn't quite as much about the 680 on the Internet as there is on the 8800.

It powers on, but I don't think it quite works properly.  The data LEDs don't change regardless of the position of the switches, and HLT/RUN doesn't change the status of the HLT/RUN LEDs.  RESET also doesn't do anything either.

The inside of this particular unit has one expansion board, with room for two more with the addition of two more slot connectors.  The expansion board has an 8x4 bank of 2 kB SRAM chips providing an additiona 64 kB of RAM on top of the 1 kB that the 680 comes with.

Based on the date codes on the integrated circuits, I'd guess this unit dates back to about 1976-1977.  It would be another 7 years or so before I laid hands on my first computer (an Apple ][+).

It's probably going to take a fair bit of work to get this unit running again.  It's by far one of the more complex pieces I've tried to work on restoring.  I've checked the voltages in a few places, but aside from that I probably won't be doing anything with it yet.  Need to acquire a few more pieces of test gear before I try to tackle something like this.