I'm trying to think "outside the box" (or maybe just "out of my head") here. Is it possible that the circular emblem on the headlight bar is not an emblem, but a siren? Like maybe for a government official's limousine?
Then there's the radiator/grill shield. If it (and whatever it is on the light bar) was removed, this angle photo would have a very different appearance. More like the attached photo of a 1934 Hispano-Suiza. Yeah, I know...there's the radiator mascot that's conspicuous by its absence, but then looking at the photo, if it had, say a Lalique mascot and the chauffeur was preparing to drive Madam et Monsieur somewhere of little importance on a winter's day, perhaps it was replaced by a dull and boring, merely functional cap.
The only thing I haven't been able to identify is the sculptured fenders. Most of the Hissos I've run across have fenders that don't extend nearly as far down on the front edge. I don't know if this is a characteristic of a certain coachbuilder or not. If it is, that might account for it.
I've gotta quit searching for this on the web and leafing thru books and get to work on my race car.
RtR
(out of the box and out of his head)