1. Front and rear shells (aluminum housing) have a cast in date code "clock" divided into twelve pie shaped segments. These are the months of the calendar year. Each segment that has dots inside represents a cancelled month. For ex. three cancelled segments would mean the part was cast in March. In the middle of the monthly segments is a circle with two digits representing the year of manufacture. Depending on the casting plant the the date code clocks are well defined or barely legible.
2. The critical date for the restorer is the assembly date which is stamped, not cast, into the rear shell. It can be found by looking for the flat cast area located near the positive battery connection. There will be a part number, three digit number (assembly plant info?), then the assembly date. This consists of a single or double digit week of the year followed by the last two digits of that year. An example would be 39-69 or the 39th week of 1969. I know it needs pictures but they'll have to wait.