McIntosh Record Compensator found in attic

I was in the attic and found a piece of history. Now what is it? It's a cute little thing. Body is 10 1/8"w, 3 3/8"h; 7 1/4"d Gold faceplate Looks as thou it could be rack mount not pan lock. I can tell it is a preamp oringal 6 pin amp plug, for MC 2100 I would guess. But thinking it is for generation before that line came into production. What is the best way to clean and test it. Looking for good advice. There seems to be light pitting on chrome top but still shinny access door to 3 tubes. Thanks Don