PU-822A/T was part of TMSS Medium system and would have carried an MX shelter when issued. It should be an 18kW generator with a 5ton (60,000Btu) ECU.
Looks like you are missing the tarp that covers the ECU but the fabric covers at there for the duct ports. You will need ducts to get the conditioned air from the ECU into the shelter where ever you choose to use it.h
When issued it should have had a ground rod kit and a sliding hammer with it, have a good look around if you can..maybe still on system? Also would have had a 60amp power cable and a distribution box but that is likely long gone..
Good luck
Poccur