Its a fake.Denver wasn t settled till much later. Nor did they have a mint. The mint opened in the early 1900s.Sorry.Still might be worth something....to some hardcore collectors.
It sounds very much like the commemorative tokens that came with recent Denver mint sets. 1789 was the year the US Treasury was founded. It would not have much value as they are very common though it seems they can fetch a couple of dollars on eBay. I hope that helps.
that could be worth hunderds of thousands of dollars