The Hammond Leslie Age Determination List

How old is my Hammond?

This is one of the most commonly asked questions, and unfortunately, due to the lack of available factory records on production dates, one of the most difficult to answer. There is some help available however:

The Hammond/Leslie age determination list was initially compiled by ?BevisPeters, and is currently maintained by RickPrevallet. It is basically a list of dates and serial numbers for various Hammond and Leslie models. It also provides guidelines to determine, generally, the age of a Hammond, based on certain features and characteristics that changed throughout the model history.

http://users.solve.net/~rickp/Hammond/AgeList.HTML

EIA Codes

Many of the components found in Hammonds and Leslies (like speakers, tubes and capacitors, for example) have numeric codes stamped on them which indicate the manufacturer and/or the date of manufacture of the device. 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:

http://www.triodeel.com/eiacode.htm#speakers

http://www.webervst.com/morecode.html

Transformer Colors

The color of the power transformer can help date an AO-28. They came in two colors: silver (pre-1963) and black (1963 and later.) Black transformers have a four digit date stamped into the bell housing.Silver ones do not. To get an idea of the production date for a silver AO-28 look at the can capacitor's date code (235-xxxx).

There's an older version of the age determination list at

http://www.mitatechs.com/techline2.html