All Philadelphia batteries shipped prior to April 1, 1920 and all batteries shipped from depot stock after this date carry double letter branding. The first battery is the factory date and the second letter in this code indicates latest month during which the guarantee may begin.
Batteries sold direct from Philadelphia to all classes of customers after April 1, 1920, carry the single letter branding code, indicating month of manufacture.
The letters used in the double letter age code are selected from the table given above, and the second letter is the important one, since it gives the latest date from which adjustment can be made. If a Philadelphia battery with a double letter age code comes in, therefore, the foregoing table should be consulted in determining the age of the battery.
If a Philadelphia battery with a single letter age code comes in, the following table should be consulted in determining the age of the battery:
Prest-O-Lite Age Code.
All Prest-O-Lite batteries carry a date letter stamped on the cell-connectors. This letter indicates the month and year in which the battery was manufacture. The letter is preceeded by a number which represents the factory at which the battery was built.
Prest-O-Lite Factory Marks.
Indianapolis—50 Cleveland—7 San Francisco—23