Grading proofs by pictures is so hard to do - and your pics are especially dark - Yours is just the average run of the mill 50's proof coin. You couldn't tell if it's a 64 or a 67 - and the price really doesn't matter because back in the later 50's and early 60's, the only way to have a desirable price increase is if the coins were CAMEO - or the especially desired DEEP CAMEO, which were only the first coins minted from fresh dies due to the "Pickling" process the proof dies went through before being installed into the minting presses and having the "First strikes" coming off of them.