Quote Originally Posted by cradeldorf View Post
Where does the "D" fit in then? I think it was "C" till 57 and "D" to 63.
My "E" is stamped 64.
As far as I can tell, the Ds were in the catalogue in '57, gone in '58 and replaced with 605s. You could still buy a 604D if you knew about them. I'm guessing they made the "604D" until the "604E" came out. So the 604Ds were 1957-1963 mostly as a special order only since they were not advertised.

Someone just got a deal:

http://www.ebay.com/itm/Altec-lansin...item3f22ab7442

After further review: a 1958 ad that shows 604Ds

http://www.ebay.com/itm/Altec-Driver...p2047675.l2557