The 1956 proof sixpence, unlike the 1955 is the more common of the two special strike types with a mintage of a 1000 leaving 506 for the specimen strike. The coin is distinguishable by a mirror finish overpowering a cartwheel finish while the specimen strike has a shallow finish with stronger cartwheel characteristics. Strike depth is also different with the proof strike having fully formed details and the specimen strike having a slightly weak star and hairlines of Queen.
The 1956 proofs have survived well with many high grade examples at PR66 and beyond. Considering their affordability and availability, collectors should aim for at least PR66 though prices go up exponentially beyond this.