The second of two types of Counterfeit Coin Detectors that Edward Kronenberg applied for patents for in 1877. This one measures 108 mm X 48 mm X 46 mm. A cast iron box with a brass top soldered on. According to U.S. Coin Scales and Counterfeit Coin Detectors (1999):
"The top has two circular cut out openings to receive U.S. 25 cent and 50 cent pieces horizontally and two small slots, each the width of the coin in question. Inside the box is a rocker to receive the coin. A coin of proper weight will trip the rocker and allow the coin to slide through. Stamped on the top are the words: PAT. APP'D FOR, COIN DETECTOR, and a U superimposed on a reversed S."
This example is in approximately Very Fine condition, with a few areas of minor discoloration and slight patina.