The date on the early FM tokens is the date of issue... 1966 in this case. In that year, Tropicana had 500 extra presentation Proof tokens made; these were in addition to the 500 in the collector sets that year. These were silver-clad and would be the easiest to gold-plate. My guess is the casino had a quantity of these left several years later and sent them out to be gold plated (if the plating is gold). Janice does not list a gold plated Trop for 66, but she does list plated tokens for other casinos.

It would be worth a premium to a token collector who wants all the Nevada tokens. My guess would be somewhere in the $5-25 price range but I don't recall seeing one of these for sale.