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.
The next number is the year of manufacture and the last two numbers will be the week of manufacture.
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.
The number 371 indicates Altec Lansing and 794 represents Harman Kardon. The first two digits after the manufacturer three digit code indicate the year.
Speakers made before the 1970s only have one digit representing the year which is misleading.
Note that sometimes a hyphen appears between the three digit manufacturer code and the date code.