Dave, the fact that there was an Imperial Athletic Club (I agree on the AC) in Dayton is not enough. I'm sure Alan and Gene would agree. I need a matchbook cover or maybe a newspaper article. I'm sure ther were other Imperial ACs. If you notice in chips I have attributed in the past, there are usually several bits of evidence, no one of which one have been enough to attribute. It's like in court. Enough circumstancial information is needed to convict.
You may very well be right with Dayton. However I really can't move my chip to Ohio without enough information to feel confident I'm right.
Now having said all that, The El Cortez 5 is Vegas. The Pals Club and Sphinx are Reno. I'm am almost sure the Pals is Louisiana. However, since its in the "book". I don't see it coming out. Too much money at stake. I've never seen evidence of the El Cortez or Sphinx attribuyions either.