Instructions
Look to see what the item. For example, a gold-plated pen might have some value because there are collectors of specific types of pens. Similarly, there are collectors of gold-plated costume jewelry. On the other hand, cigarette cases are likely to be worth very little, because as of 2011 they play little part in a modern lifestyle.
Ask yourself whether you might be looking at a novelty item or limited edition. Some items, such as cellphones and toys, are not usually associated with the gold-plating process. If they are plated, it might be a sign that they are special in some way, perhaps issued in small numbers for a particular occasion. If this is so, they will almost certainly have some value.
See if the item carries a brand-name or maker's mark. An item is much more likely to have some worth and, obviously, it's much easier for you to research if it isn't anonymous. In the case of costume jewelry, there are many sought after makers whose names will add a premium to an individual piece.
Type any brand names and maker's names, along with the words "gold plated" and a clear descriptive term such as "model car" into the search engine of an online auction house. This should help you to find lots similar or identical to your own. Doing this should give you a broad sense of what your own item is likely to be worth.