It's the control box for the power in an MSQ-85B shelter. Quoting from an article I found,
"AN/MSQ-85B Mobile Audiovisual Information Collection and Dissemination System. Few of the AN/MSQ-85B still exist in their original configuration, and these are more museum pieces of 1970s technology than usable equipment. The AN/MSQ-85B includes an AQ-4A movie projector, AN/UIH-6 public address system, AP-9 slide projector, AN/USH two-track international standard tape recorder, BM-22A large projection screen and R-520A/UUR radio receiver. "
PS, I got one of them too. Mine had the Camp Victory customs form still in it, clearing the shelter to come back to Ft. Bragg.