this got no response when i posted it just before christmas, but this time i hope our bexley experts can chime in to help me figure out this happy discovery.
the bexleys arrived today (here in the philippines)--happy new year!
they were even more wonderful than i imagined they would be, and i'll show why, but first, a pic of the two pens:


you'll see that one is bigger than the other (something i didn't expect--they were sold separately, so i never saw them side-by-side before this). i'd soon see the sense of the difference in size.
i can now see why the seller thought that they were a mix of bexley and parker parts--they're actually all bexley, no parker at all in them, but just as i suspected, they're the size of the parker duofold centennial (the red one) and international (the titanium), respectively--and more than size, they're threaded to receive and to use the sections and nibs of the duofolds!
here's the red bexley as is:

and here it is, with a section and nib from my greenwich centennial:

here's the bexley and the centennial side by side (i didn't take a pic, but the same holds for the titanium bexley and the international--same size, same swap):

and as a final, fun touch, i decided to replace the generic steel schmidt nib (it didn't even have the bexley name on it) on the titanium pen with what i think should be the perfect replacement--a stipula titanium 1.1 nib, which i just happened to have lying around. so now it's truly a titanium pen with a nib just also happens to flex beautifully:

nice, too, that the pens were priced very reasonably (i wondered why no one else picked them up, as they had been on buy-it-now for quite a while). now i really want to know from the bexley experts here if they'd encountered these models before, or if they might be prototypes, and also if other bexleys have this same amazing swappability with parker duofolds (which i also collect, so i guess i'm in luck parts-wise).
thanks for looking!