Types CP-3 (1906 to 1908), CP-4 (1908 to the 1920s?)	Back	Up
The CP-3 was a redesign of the CP-2 using the Form 4 prepayment device instead of the Form 3 device. The CP-3 had the knob mounted on the prepayment mechanism, but any strain on the knob was prone to damage the mechanism, so it was soon superseded by the CP-4 which had the knob in the cover and had a notch on the back that operated a lever on the mechanism. The space above the register in both versions was for a scale showing the number of coins remaining to the user's credit.	Electrical Meterman's Handbook