Magnetic Peripherals Inc Field Test Unit
The device is used to diagnose and repair DEC RM02 & RM03 disk drives. Model 9762 disk drives were made by CDC/MPI, and sold to DEC. DEC added a Massbus interface to the drive and sold it as the RM02 and RM03. The only difference between the two drives was the speed that the disk spun. The faster RM03 drives could only be used on the PDP-11/70 and the PDP-10.
An interface board that is stored inside of the tester was plugged into a special slot in the drive, and two cables were connected between the drive and the tester. A special disk pack was installed in the drive. The special disk pack had tracks written that were not concentric, and were used to check the alignment of the read/write heads. The meter on the tester would show microinches of misalignement on the heads. The switches on the tester would let you send commands to the drive to test that seeks worked OK, and perform other functions.
You can see the analog interface board in the static bag at the bottom.
If you look through the slits in the sheet metal in the middle, you can see the control cables that connect the tester to the drive.