Sinstered and copper planchet are two totally different things. Sinstered is imprprerly annealed & copper planchet is just that.
Here are some estimated values on the 1950's proofs. These are for raw coins. They sell very easily and at good prices. It all depends on the eye appeal, cameo, etc.. 1950 PF : $25-$60 1951 PF : $20-$60 1952 PF : $15-$40 1953 PF : $15-$35 1954 PF : $5-$12 Then the values drop significantly. The only proofs that have more value are the early proofs (1939-1942).
Proof Jeffersons, including the mid to late 50s proofs, can be found for $1.25 - $2.00 most anywhere, for PR60-PR64, and maybe 65s; raw.