Looks like a typical tach/dwell/volt meter. Basic hook up would be the smaller alligator clips, red to batt +, black to batt -. Larger alligator clip to coil - and the large open center clip over the #1 spark plug lead.

You just missed a manual and device on ebay by a couple months, but if you're bold enough you could write the seller a question, find out if he'll put you in touch with the buyer, and ask if that guy will send you pic/copy of the manual. Long shot, but nothing good comes without effort. https://www.ebay.com/itm/38539400579...p2047675.l2557