Manchester Reader Writer 4523H system building block
There is a piece of masking tape on the side of the module explaining that the block no longer functions.
Digital Equipment Corporation (DEC)
||Printed on the solder side at the insertion end
||Stamped into the face of the aluminum frame
||Stamped into the side of the aluminum frame
overall: 1/2 in x 7 in x 4 1/2 in