1942 Catalog plus 1943, etc.

[Elitopus1]

According to the technical audio data, the 605 was a speaker cabinet produced in 1946. Then like Bowtie said, it later became the 605 Duplex

[Steve Schell]

Yes, apples and oranges. The first Duplex was the field coil 15" 601 of 1943, soon followed by the permanent magnet 604 of late 1944. In the mid to late 1940s there were 605 and 605A cabinets for use with the Duplex. Later, 1960s, the downgraded 605A Duplex replaced the 604D for a time until Altec realized their horrible mistake. Then the 604E "Super Duplex" made its debut and the lower cost 605B remained in the line as a cheaper alternative.