Dating "Any" Amp

Common Potentiometer Source Codes

Code	Manufacturer
106	Allen-Bradley
134	CentraLab
137	CTS
140	Clarostat
304	Stackpole
381	Bourns Networks

Common Speaker Source Codes

Code	Manufacturer
67	Eminence
73	JB Lansing (JBL)
137	CTS
220	Jensen
308	Stromberg-Carlson
328	Utah
336	Western Electric
391	Altec-Lansing
416	Heath
465	Oxford
589	Bogen
649	Electro-Voice

Common Transformer Source Codes

Code	Manufacturer
606	Schumacher
830	Triad

How the Source-Date Code Works.

The source-date code on a pot is a 6 or 7 digit code impressed into the casing of the potentiometer. For speakers this code can be 5, 6, 7 or 8 digits long, and it's ink-stamped or paint-stamped on the "bell housing" of the speaker.

In either case, the code works the same. The first 3 digits on a pot, or the first 2, 3 or 4 digits on a speaker are the source or manufacturer code.

The remaining 3 or 4 digits are the date code. In 3 digit dates code, the 1st digit is the last digit of the year. On 4 digits date codes, the 1st and 2nd digits are the last two digits of the year. In either case, the remaining 2 digits are the week of manufacture (01 to 52). With this in mind, remember if the last two digits of the source-date code are greater than 52, you're not looking at the source-date code!

Also it's worth mentioning:

• Sometimes there is a space or hyphen between the manuafacturer code and the year/week code.
• 3 digit date codes were used in the 1940's and 1950's.
• 4 digit date codes were used in the 1960's and later (this makes determining the year much simplier!).
• On 3 digit date codes, you have to "guess" the decade of the pot or speaker. Usually this isn't too difficult.

Examples of Source-Date Codes.

With all this information in mind, can you identify the following manufacturer and date of these source-date codes?

220 7001

Jensen speaker, 1st week of 1970.

137341

CTS, 41st week of 1953 (or 1943 or 1963, but probably 1953 as source-date codes weren't used much during or before WWII, and 4 digit date codes weren't used till the 1960's and later).

304-6110

Stackpole pot, 10th week of 1961.

137848

CTS, 48th week or 1948 or 1958.

4656755

Not a source-date code. Can you see why? If you can't, read the above information again!

Less Common Source Codes

Code	Manufacturer
24	Becker
101	Admiral
119	Automatic Mfg
125	Bendix
130	Panasonic
132	Talk-a-Phone
145	Consolidated
150	Crecent
169	Hitachi
185	Motorola
188	General Electric
213	Dearborn Wire
230	Littlefuse
232	Magnavox
235	Mallory (North American Capacitor)
245	National
251	Ohmite
252	Dukane
260	Philco
270	Quam-Nichols
274	RCA
277	Emerson
280	Raytheon
285	Rola
286	Ross
296	Solar
312	Sylvania
343	Zenith
371	Best
381	Bourns
394	Foster Transformer
433	Cleveland
449	Wilder
446	Delco
549	Midwest
575	Heppner
706	Pioneer
719	Carbonneau
742	Esquire
748	Russel
756	Universal
767	Quincy
787	Sonatone
789	McGregor
794	Harmon Kardon
795	Atlas
828	Midland
840	Ampex
847	University
918	Oaktron
1056	Fisher
1059	Channel
1098	Pyle
1113	Acoustic Fiber Sound
1149	Curtis Mathis
1191	Micro Magnet