I may be wrong, but I doubt if you can find a refiner that would accept that job. There is really no good way that I know of to process this material. However, I did come up with an electrolytic cyanide method, years ago, that worked pretty well. To use it, you would either have to rack the pieces individually or use a barrel plater. A second possibility is to use the sulfuric stripper - however, you'll have to figure out how to get the silver out of the sulfuric. Thirdly, you could use hot 95 sulfuric/5 nitric, but that is dangerous, slow, and probably expensive.
Here's a list of the various standard specifications of silverplate from the Butts and Coxe silver book. I don't know whether the items are stamped this way, or not, but I think many are.
Half plate - 1 tr.oz. of silver per gross (144 pieces) of teaspoons
Standard plate - 2 oz/gross
Double plate - 4 oz/gross
Triple plate - 6 oz/gross
Quadruple plate - 8 oz/gross
Federal Specification - 9 oz/gross
The silver thickness on these ranges from .00015" to .00125". At a $27 silver spot, that figures from $0.022 to $0.187 per square inch of surface area.
BTW, here's an easy new way to convert plating thicknesses to dollars per square inch.
For Gold: (plating thickness in inches) x 10.18 x spot price = $ value/square inch
For silver: (plating thickness in inches) x 5.53 x spot price = $ value/square inch
Why this works:
Please note that the plating thickness in inches = the number of cubic inches of one square inch. Example: .00015" x 1" x 1" = .00015 cu.in.
A cu.in. of gold weighs 10.18 tr.oz. A cu.in. of silver weighs 5.53 tr.oz.
In practice, the values run slightly less, since the density of plating is always slightly less than the theoretical density, due to alloying ingredients, inclusions, and/or porosity.
