The best way to determine the value is to use a plating calculator like this: Gold Plating Calculator

The hard part is finding the thickness of the plating, which is why we need to know what they came from. Talk to Etack, he is really good with this type of info. I think the Gold refining forum also has a list of applications and the typical plating thicknesses that are used. I would not recommend posting anything or asking them any questions, just search for the info.