Numista lists this coin (N#480021) but with no image. I personally do not have the coin, but I have seen an image of it at the following website: Guyana - Guyana. Proof gold 500 Dollars, 1994, commemorating the Royal Visit, February 1994.
It looks like a beautiful coin but with the price of gold today it is really expensive and impossible to find. I do have the $50 dollar version in silver which is N#113392.