Common era dating system
These codes have been used on components including potentiometers (pots), transformers, capacitors, tubes, and speakers.
The code usually consists of 6 or 7 digits such as 137634 where the first two or three digits is the EIA code for the manufacturer (137 denotes CTS), the fourth digit and sometimes fifth digit denotes the year (in this case it could be 1956, 66, or 76), and the last two digits denote the week of the year.
These codes can be found on speakers, transformers, pots, capacitors, and multi-section electrolytic "can" caps.This information original was found on The Unofficial Ampeg Page ( which appears to be dead.I pulled this information from Google's cache of the site. D." stands for , Latin for “in the year of the lord,” and refers specifically to the birth of Jesus Christ. C." stands for "before Christ." In English, it is common for "A. In the early Middle Ages, the most important calculation, and thus one of the main motivations for the European study of mathematics, was the problem of when to celebrate Easter. Computus (Latin for computation) was the procedure for calculating this most important date, and the computations were set forth in documents known as Easter tables. Dionysius devised his system to replace the Diocletian system, named after the 51st emperor of Rome, who ruled from A.
It appears that the serialization system used during this time period is date encoded which makes dating the amplifier rather easy.