Bally Bell [Double Bell] [Model 157] © 1939 Bally.
Released in January 1939.
Machine's picture.
Collector's Treasury of Antique Slot Machines from Contemporary Advertising - Peter Bach - Page 228 & 229
Collector's Guide to Vintage Coin Machines - Richard M. Bueschel - Page 51
The Coin Machine Journal - January 1940 issue
Loose Change Blue Book for Slot Machines [4th Edition]