Events have been held in various locations. The Worthpoint link shows a number of different year chips. I wouldn't call it a "casino chip", but maybe you could call it No Cash Value. I doubt it was used to wager with, though. Cost of a plate to these dinners was several thousand dollars. The 5000 could have been a kind of receipt for your donation. Don't know about the lower denoms like 25 though.

This chip has been posted on The Chip Board several times in the past. There's even a post by Greg replying to one of them.