I found an interesting thread here on a record forum:
http://bsnpubs.websitetoolbox.com/post?id=84340
Which contains a link to a paper with info on 16 2/3 rpm records (about 2/3 of the way through the paper):
http://78rpmrecord.com/altformat.htm
Many different formats of 16 rpm records seem to have preceded the "Highway Hi-Fi", including some as large as 22" for background music. Dr Goldmark perhaps was the first to use the very fine pitch groves ( 0.25 mil stylus). I think that I once saw a boxed set of 16 2/3 records mixed in with boxed sets of 45s... these records had a huge center hole, about the size of the label on a 45. Guess I should have bought the set.
But, getting back to the DuMont, That is a GREAT find (even if the changer does not play all 4 record speeds that were available at the time !
) I am still stumped about the tape deck, the head and pinch roller covers resemble the shape of those used by Tandberg, but the photo does not appear to match early Tandberg machines. Did DuMont make the deck? It will be interesting to see if there is any identification on the unit itself.
jr