4 inputs D.C. sense amplifier 4552D system building block
The object has a green board surrounded by an aluminum frame and a blue plastic connector. One side of the board is covered in components, including resistors, transistors, diodes, capacitors, and two transformers. There are three inspection stamps toward the extraction end. There are also three inputs screwed to the frame at the extraction end. The solder side has a printed circuit with a grid lettered A-Z.
Digital Equipment Corporation (DEC)
Printed on the solder side at the insertion end of the board