An impression made during the production of stamps. For use only by printers and postal administrations, these are not available to collectors.
Impressions of a print. In the case of an incomplete print they are referred to as "working proofs."
Coins which are minted by the government specifically for collectors and never introduced into circulation. Proof coins are struck multiple times on specifically detailed dies, which elevates the sculpturing and accentuates the detail. The backgrounds are highly polished for a mirror-like finish. Proof coins can be graded using the same Sheldon system but will have the designation PR for Proof instead of MS (Ex. PR70).