This whole set of nomenclature is sort of just a revisionist history thing. The "DX" frames are so-named b/c,
usually, in the catalog they were labeled with the letter "d", a few digits, and then the letter "X"... eg, the D97X. In 1950, however, the frames where both the top- and mid-tube were curved (which Schwinn ppl almost universally call "DX") was called the D-13. (No "X," that year.) In 1950, the frames we call "Straightbars" came in a feature-laden "D-19" and a stripped-out, entry-level "D-12". Later "straightbars" tended to have real names (eg, "Hornet") instead of the alphanumeric names. Basically, Schwinn made a couple frames, and offered most frame styles with different components, to create different models with their own unique spec, names, prices, and (sometimes) paintjobs.
Here's a good resource for trying to sort this stuff out; just remember that not every model is represented in the catalog, that spec would sometimes change between what was listed in the catalog and what the dealer received, and that some of these frames may have been made one year, but actually built and released the next...
http://schwinncruisers.com/catalogs/
Sorry if this disrupted your F/S thread, but this thing is such a hott deal, it sold in a few hours... so i don't feel
too bad about it...