So it looks like Iceman was correct about the model, DD78 (see below). Went and picked it up today. Total cost: $400 + $40 for gas for my brother's truck.
The seller told me it is about 6 or 7 years old, but it was plugged in and cold. All the fans work and aside from being kinda grimy, it's in good condition. The door seals probably need replacement but it's not urgent.
Pics (after my roommate cleaned it up with some 409).
Regulator on CO2 tank (not sure what this means but it was pointed at 10)
