The only thing referring to Howard Hughes (that I'm aware of) is the H.N.O. (Hughes Nevada Operations) initials on those Sands chips ($5, $25, $100). Of course, you know about those.

It seems that Hughes wanted to keep a low profile, the opposite of Del Webb and others with their names on lots of stuff.

After Summa Corporation was formed, it was the vehicle he used around Las Vegas, and it was owned, in turn by Hughes Tool Company, I think (but haven't double-checked that).

The only thing that might reference him by name might be stock certificates or incorporation papers, etc. for Hughes Tool, Summa Corp or even his forays into owning Hollywood studios and such. But none of those were publicly-held companies, so unless you go to the Nevada (or Texas or California) state records archives for business filings, it will be hard to find his name on anything, IMO.

I guess that goes with being the world's most famous recluse.