i broke two oldschool revvys off at the feedneck, i have also had a shake and shoot crack.
How old school are you talking here? I've got one that's from 1997-98, and the plastic is still plenty flexible (came with an opaque lid).
As for the new JT one, It looks like they took the mold used when the made Viewloader Revolutions with X-Boards (those came out when they switched to the polycarbonate bodies):
You can see the same indentation around the 'label' on that loader on the JT version. The original revolutions don't have that indentation and their logo is cheesier than the newer revvies.