The 6 digit code indicates what manufacturer made the speaker and when it was made. Here is a list of some of the speaker manufacturers and their EIA codes: So, the speaker in the image above would have been made by Jensen (220) during the 27th week of 1951 or 1961.
The year is confusing because it is only a single digit.
Here's a quick and easy guide to help you understand the rim numbers which reveal a speaker's manufacturer and its production date. The speaker reads C10N C7438 5 on the right: which describes the model and its construction.
But what about the 6-digit code 220438 to the left?
Some manufacturers also attached other letters to the end of the date code to indicate day of the week, work shift, serial number, lot number, etc.
The EIA only specifies manufacturer and year/week code.
It'd be awesome if you could upgrade to a modern browser, especially Chrome and Firefox as that is the best out there right now. You might find some of the information useful in determining which speaker would be best suited to your application.The picture is a section of the basket rim of a speaker.