One major difference with the A807 and A810 is that the A810 has all the circuitry split into small cards. The A807 has one single card for all transport functions, plus daughter cards for the audio systems. However, the A807 MK2 was the last model off the production line around 2001, so it may possibly be in very good condition if it's one of the later ones.
Do you know if it's a Mk1 or Mk2? You might also ask the seller what the display says when the machine is first powered on - it shows the date of the system software. Mine is an early model and the OS reads "30:88" which I believe is mid July 1988.
A nice feature is that they can be calibrated electronically, and you can jot down the original calibration values and re-enter them if you mess up.
All in all, they are nice machines but some people say the A810 sounds better as well as being more modular. The A807 is not much fun if it needs maintenance. I've had to re-cap the audio boards on mine, but it's now finally working properly.
Things to be aware of:
* It uses balanced XLR. No RCA/phono cables.
* Not all models have meters. Mine was designed to be plugged into a mixing desk so I had to rig my own meters for it.
* There is also a playback-only version - avoid that if you want to use it for recording.