Also note that those have the very flat rolled steel backplate with full size foilcal. The later(seemingly preferred) version has the rounded cast(i think it's cast) backplate with the threaded holes and recess for the smaller foilcal like the ones in your OP.Quote:
Originally Posted by Old Guy
These also appear to have "tires" on the edge of the ferrite: http://www.wardsweb.org/audio/Altec/Altec28.html
