My guess is that this item is unsigned valued at somewhere around $30 or $40, signed by relatively unknown model, add $20 or so dollars.
Go to eBay and look the item up. When you see similar items for sale and the going prices, you will have a sense of the value.
Coke memorabilia is quite common, and that makes the items less valuable. Condition of the tray, rarity, how well known the model is are all factors contributing to the value.
Also, and this is important, provenance that can be proven with written documents, photos, etc. can contribute mightily to a collectible. For example, if the tray belonged to Elvis and you can prove that, then the item is suddenly worth at least 10 times its original and maybe more. Especially if the provenance is verified with a photo, or list of estate items, etc. If the provenance can be included with the piece, the value will sky rocket.