Never heard anything of it myself. Ever do a GOOGLE Search?

First, "641 N. Clark St." appears to be an address for a Walgreens today.

As for "French Casino", I find listings that mention a Jazz Club, an eBay listing for matches and a PBS website mentioning the Dillenger spending his 31st Birthday with Polly Hamilton there.

I didn't open any of the links but there might be some interesting info there for you to look at.