VINTAGE Pair Altec Lansing 603-B Speakers 1951 15" Dia-Cone Great Condition! | eBay

Haven't seen a pair of these in a while -- I would think they're probably pretty rare (in good condition)...... Anyone ever heard a pair of these? Judging from the specs and graph in this link (below), it's no 604. I see it's a diacone, what's the difference between that and a duplex?

http://www.lansingheritage.org/image...1949/page4.jpg

A lot better price than this one:

Altec Lansing 603B 15" Dia-Cone RARE! Speaker 8 ohm 25W | eBay