JAN tubes usually had the contract number, the production or test date and the manufacturer name printed on the boxes. Commercial tubes used a variety of obvious or covert codes. At Westinghouse, we used an alphabetic code. The first letter was the year, then the next letter was the week of manufacture. Since there were 52 manufacturing weeks in the year, we re-used the letters and changed the year code. This was used on semiconductors; I don't remember if the Tube Division used the same. I think there are tube collector sites on the Internet with some of the mfrs. date code systems explained.
Rich
: Does anyone know whether early vacuum tubes, say early 1930s and newer, had date codes on the base? Some tubes I have purchased seem to have dates but that might be a lot code or something. I know that the modern method for components is to code them with 4 digits representing the week and year. One tube I bought recently was a JAN component so it had the date on the box. Tough to remember what was happening 50 or more years ago.
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