Are there any pre 1800 silver coins that could be had at or extremely close to spot? I think it would be so cool to have an antique box with maybe 10 ounces of medieval or whatever coins that were bought near spot.
Only ones I can think of, (short of truly junk, ag, damaged pieces), would be Maria Theresa restrikes. They have a date in the 1700's, though have been restruck continuously since then.
Well, even old Mexican half reales, which used to be darn close to spot, are bringing better money nowadays if not holed. I simply cannot think of any 18th century or older coins not worth well over spot unless damaged. Even 19th century is getting harder to find ok coins at melt. I think too many people would like to do exactly what you would like to do.
About 20 years ago I bought a Mexican 8 reales from 1782 out of a junk box for $5 - it was damaged because of all the Chinese chop marks all over it. Now it is a collectable because of them. Worth quite a bit more than I paid for it, prolly even slab as it has a nice NT colour.
Oh and back then you could still find Barbers from the 1890s on up to 1916 in junk silver lots. Good luck now.