Vintage Motorola model 12AT03, 0-3000rpm tachometer as shown above. Tach is 3 3/4 in diameter across the face and 3 5/16" in diameter in the rear. I got this with a load of semi truck parts and have no idea, what is was used on originally or  if it was aftermarket. For the price, if you need a 3000 rpm tach you cant go wrong.