The Hammond & Leslie Age Determination List

Mission Statement

To help determine the manufacturing date of Hammond organs and Leslie speakers.

Use this form if you would like to submit your Hammond organ for inclusion in these tables. When you hit the “Submit” button you will see a message advising “Update Successful.” Your information will be placed in a holding area for review and added to the age list after acceptance. To include a Leslie speaker or Hammond tone cabinet, see the Acknowledgements section below. Please include an email address so I can contact you if I have a question.

Discussion

“How old is my Hammond organ and Leslie speaker?” Read on and you may learn the answer! Beginning in late 1935 and continuing to mid-1975, the archetypal instrument we think of when hearing the word “organ” was produced by the thousands. 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. This information is being compiled, organized and edited into a soon to be released book that details all sorts of production and manufacturing information, including tables showing serial numbers and their date of production. Some of the entries on the age list show actual known production dates and can be used as markers to gauge the quality of other entries around them. Until this work is published, the Age List will continue to function more or less as it has; a quasi-definitive source of this information and a registry of Hammond and Leslie product owners.

Thanks to the Electronics Industry Association (EIA) code conveniently placed on them by the manufacturer, many individual components can be dated to the year and week of production. Due to Hammond and Leslie purchasing components in large quantities, using these codes as definitive signposts will not produce an accurate “born on” date. However, by examining those components as a group one can determine that the instrument was produced no earlier than the latest date indicated by its component parts. In general, tubes appear to have had the shortest stock life and speakers the longest.

Even the above is fraught with some risk, as replacement parts used for repair or modification will occasionally skew the overall picture. Additionally, some organs have been pieced together in order to get one working unit out of many; this will produce inconsistent and unlikely date code ranges. All available information must be taken as a whole, and, combined with some general tips and observations provided below, a narrow range of probable production years can be arrived at which in many cases will be accurate enough for most people’s desires.

One thing to remember in this chronological quest is these instruments were built to be played, not (in most cases) to become museum pieces. Don’t get too hung up on searching for temporal coordinates to the exclusion of the unit’s real purpose as a musical instrument.

Methodology

Some of the component parts of Hammonds and Leslies have EIA codes printed on them. What follows is a breakdown of the more common parts and a description of their codes. Some specific examples are cited that can be used to provide assistance in identifying the production date of similar components.

Tubes

Many tubes have a date code on them. Tung-Sol 6550 tubes have the following format: XXXYYWW, where XXX is the EIA manufacturer code, YY is the last two digits of the year and WW is the number of the week in that year. 3227204 is a Tung-Sol tube manufactured during the fourth week of 1972. Tung-Sol 6550 tubes made for other companies (like RCA) have a four-digit date code only. Tubes with “Hammond” silk screened on them typically have a code consisting of two pairs of numbers separated by a dash. The format is YY-WW, where YY is the last two digits of the year and WW is the number of the week in that year. In the example, 73-48 is the 48th week of 1973.

Capacitors

Many capacitors have a date code on them, but some do not. Most of the tone generator wax and Mylar capacitors do, as well as pre- and power amplifier multi-section can electrolytic capacitors. The code typically takes the form of YYWW, where YY is the last two digits of the production year and WW is the production week. 6150 would be the fiftieth week of 1961.

Speakers

All of the speakers in Hammond organs, Hammond tone cabinets and Leslie cabinets dating from 1946 forward that I have seen have production date codes stamped on them. This may also be true for earlier units. The coding scheme is XXXYWW where XXX is the company EIA code (Jensen = 220, Rola = 285, Heppner = 575), Y is the last digit of the production year, and WW is the production week. 285642 would be a Rola speaker made in the 42nd week of 19x6 (you have to figure out which decade using other information). For additional speaker manufacturer codes, see Ted Weber’s listing at Weber Speakers.

Motors

Later Leslie motors have a sticker on them indicating their manufacturing date. The formula is XXX-YYWW, where XXX is the manufacturer EIA code (190 indicates General Instrument in the present example), YY is the last two digits of the year of manufacture, and WW is the week of manufacture. In the example shown, 190-7215 was made in the 15th week of 1972. Earlier Leslie motors have a stamped four-digit code.

Leslie Cabinets

Inside each Leslie produced after 1956, on the lower baffle, is a date code (sometimes hidden by the bass speaker). Here’s how it works: you have to be able to date the Leslie within 10 years, which should be fairly easy. Just to get started, 21H’s are 1951–1958, 22H’s are 1958–1963, 122/142/147/145’s are late 1963 and later. Any other single speed model (45/47/51) is prior to late 1963. There are a number of visual cues: anything with a foil CBS ID tag is post 1966, anything with a metal tag is prior to 1966. The typewritten silver foil tags appeared in the mid to late ’70s. The new style Leslie logo appeared in 1970, and cabinets made after then have particle board baffles rather than all hardwood construction and are missing the instruction sheet formerly pasted to the back. The code consists of 4 digits; the first 3 numbers are the Julian date, and the last digit is the year. For example, model 25 serial #1522 has 1619 stamped on the baffle identifying it was made on the 161st day of 1959.

Hammond Cabinets and Components

There are several external features that can provide clues to an organ’s age.

Enumeration

Below is a compilation of Hammond organ serial numbers and dates submitted by owners and other interested folks. There are discrepancies here, so be prepared for some imprecision; it should get you within a year or two when combined with the information above. Since I can’t independently verify the information provided, this seems to be the best we can do.

Note: organs produced after 1968 had a letter prefix code in the serial number: A = 1969, B = 1970, C = 1971, D = 1972, E = 1973. Sometime in mid-1973, in the mid-200000’s, Hammond dropped the prefix letter. This means half the organs built in ’73 and all ’74/’75 organs have no letter code. Serial numbers began to take on a surreal quality at this time, with higher serial numbers not necessarily representing newer units. For example: A-xxxxx = 1969, B-(x)xxxxx = 1970, C-xxxxxx = 1971, D-xxxxxx = 1972, E-xxxxxx = 1973. Organs previously in the Age List falling in the prefix group have been removed since they readily admit their age.

Note: Confidence Level is an arbitrary rating from 0 to 100. 33 indicates a wild guess, paper documentation, bill of sale, etc.; 66 indicates matching by using the cabinet features list; 100 indicates looking at date codes and cabinet features.

• Models produced in other countries had a different serial number system.
• Units are located in the United States unless otherwise indicated.

Acknowledgements

Much of the component dating information contained here was supplied by Sal Azzarelli (Azztec Organs). Other contributors include Al Goff (Goff Professional), Harvey Olsen, and Bob Schleicher (Electronic Instrument Service). Thanks also is due to Bevis Peters and Tom Ericsson for previously administering this page.

Don Erickson performed the programming that automates the input of organ serial numbers, as well as the behind the scenes code that places the serial numbers into a MySQL database and figures out which records go with which organ model.

For more information on Hammond organs, there are two mailing lists offering discussion and insight. To subscribe, click on the following links: The Hammond Forum and The Hammond List.

This page is maintained by Rick Prevallet. If you would like to submit a Leslie speaker or Hammond tone cabinet for inclusion in the list, or have any questions, comments or suggestions, drop me a message. Links to other Hammond content can be found at the Tonewheel General Hospital.