The prop had an articulated tail, head, and front leg, operated by poles from inside (in some pics you can see the latex skin hanging open under the belly where someone climbed inside.)
The '97 design reboot and added imagery proved GL had a real love of the Dewback. Probably because the mid 1970s Ron Cobb lizard+rider painting was so inspirational. The Dewback harkens back to the core images and ideas that inspired GL to create SW.
There are quite a lot of behind the scenes pics of the Dewback (the famous promo one we all know technically is behind the scenes because it has the "look sir droids" trooper in the saddle unlike in the movie) so you can get a pretty clear view of it, as sorta funky as it was.
These rarer pics of the "back" side views of the Dewback show that the rear Tornister (WWI German backpack made of cowhide)/saddlebag on that side is actually different from the other three - it is the radio operator version, even though both SSC and now HT made all four saddlebags the same.
The pic also shows that the pole only has a bare-metallic part at one end, not at both ends like SSC and HT did. The pole also has a thin wire visible running along it, perhaps for a "sparks" special effect as the rider controlled the beast in close ups that were never filmed.
They got rid of the skinny chicken leg look, but still stuck with the clawed chicken/t-rex style feet. The Dewback prop, like the Kenner toy, had elephant/rhino type feet, so that's what my custom Dewback has.
The 12" Hasbro one from the 1990s almost seems like its an original creation by Hasbro. While the 1997 3 3/4" Dewback mimicked the SE design pretty closely, the 12" one looks quite different again. The newer 3 3/4" Hasbro Dewback (from maybe 10-12 years ago) was a similar look, but much larger in scale compared to the rider. Then for the 6" scale version they went back to something closer to the 1977 design.
This is my Hasbro 3 3/4" Dewback (from maybe 2010-2012 or so) which has t-rex legs/feet and that ugly iguana head that began with the 1997 redesign. What a bizarre thing to abandon the classic 1977 Dewback head, one of the most memorable images from the original film's release.