Altec 1218A Cabinets

[jnl636]

I just picked up a pair with 15" 421-A's inside. Numbers on the back are 50 03 030840. Can someone give me the date of these?

[Alien_Shore]

Look on the frame for a 6-digit EIA number that begins with 391.
The format of the EIA number is 391YWW.
Where Y is the last digit of the year they were produced, and WW is the week (01-52).
421A's were produced over a number of years, but Y is probably going to be in the 60's or early 70's.