Sounds like you have a pretty good start on a collection.
I collect and research illegal casinos from all over the US. Have well over 2,000 different with ID's and boxes more to research when I get around to it. There were 1,000's of illegals pre 1961 accross the country and they are rich in history, many with ties to Las Vegas.

Just came accross a "Cluster" of new illegals in Decatur and Clinton, IL.

I was born and raised in Newport. Got out of the Army in 1961, just as the "Era Of The Illegals" was ending. I fancied myself a poker player, and the operators of the illegals played poker regular. I played with them all thru the 60's and 70's. They had many great stories to tell. I started collecting their chips in about 1962.

Here is some research on The Arrowhead Inn.
http://www.marlowcasinochips.com/links/genetrimble/genetrimble.htm

Moved to Las Vegas in 1980.
Will reply to your email in a few minutes.