This list is circa 1955, and some codes have been reassigned or added since that time.
Code formats were not completely standardized, but a little deciphering will generally yield the info of interest.
It also provides guidelines to determine, generally, the age of a Hammond, based on certain features and characteristics that changed throughout the model history.
It is basically a list of dates and serial numbers for various Hammond and Leslie models.
The age determinination list contains good descriptions of the various formats these code take.
Additionally, these lists of EIA manufacturer codes may be of use: The color of the power transformer can help date an AO-28.
Please include an email address so I can contact you if I have a question. With a production history covering more than forty years, determining the exact manufacturing date of tonewheel Hammonds used to be difficult; new models were not introduced every year and production changes that were made were often subtle.
Recently, the production data was found and there is no longer any need for guessing.
Plus the OLDEST Hammond verifiable installed product will win a 0 (US) prepaid credit card.