TUBE CODES

The 58-39 most likely means that the tube was manufactured in the 39th week of 1958. Likewise for 58-17. Not sure about 4-39 and 5-22, but perhaps the last two digits of those numbers also refer to the week, and the 4 and 5 also refer to the year, but with the first digit of the particular decade omitted.

Regards,
-- Al

Check out the code links archived on tube Asylum. Just do a search.
The single digits were used by other manufacturers to designate a year during the 1950s. Thus Almarg appears correct the second set seems to mean made in the 39th week of 1954 and the 22 week of 1955. The first two look like JAN codes both tubes 1958 the 17th and 39th week.

Thanks for the information.