Who made the catenary....

Good evening (morning technically):

That looks a lot like one of Model Memories PRR offerings, or it is a scratch build.  I have seen several good examples of scratch-built Pennsy catenary, for the same reason you stated:  simple and elegant, which was often the case with the Pennsy itself.

EDIT:  I found a better video of the Brandywine system here.  That catenary has a scratch-built look to it the more I study it, with a nice static shot here.