I just acquired the $500 Mint chip shown at the bottom right. It is a used chip, and although I dont usually 'clean' I did so to get a good scan.
The chip has short H&C, differing from the one shown above it which is long H&C. The inserts are a good color match for both chips, the color of the chips themselves, and the word 'Mint' are quite different in real life.
The top chip, which is frequently seen, has previously been confirmed as being made for Carl Osborne after the casino closed. The bottom chip is, in my opinion, a genuine chip from the casino. It needs a TCR# and a 'nice' value. I doubt many survived. (did you get that bit Allan? )
Sorry, it is not for sale
It further confirms my feelings that although BJ and PS re-manufactured chips 'as close as possible to the originals' for Osborne, they deliberately differed in some way.

I have recently taken some time to study both Borland's Blue book, and a series of his newsletters. I managed to glean the following information which I have also added to my article.
A genuine $100 Eddies Fab 50's chip was in use at the casino. (IMO, following the pattern of the other counterfeits, the genuine chip would either have been a Burt Co LCV or with a 'non cog' shaped inlay. Maybe Jim B can look this one up for me also
There is a record of the release of a $500 Castaways Blue 'incuse' chip. The newsletter was dated 2 years before the casino closed.
No incuse examples have ever been recorded.
I found no reference to sports book chips.

The full updated article is available here:
http://www.marlowcasinochips.com/links/davidspragg/osborne/osborne.htm