The 1956 is a relatively high mintage and many were saved as this issue is readily available in Gem condition. As is the case with most later dates, the survivors include many white frosty Gems from original rolls and nicely toned specimens from original Government mint sets.
Although this date is among the easiest in the series to locate in MS66 and even MS67 grade, when it comes to upper end MS67 quality, the coin becomes fairly scarce as is the case with nearly every silver quarter in this series. Interestingly, at the time of this writing (and PCGS has been open for business for more than (25) years now), just one MS68 coin has been graded of this date. Also, of note ... virtually every coin that has achieved the MS67 grade level is a mint set toned or album toned specimen. Blazing superb gems from original rolls (without toning that can often hide imperfections) generally max out at MS66 grade. In my near (25) years of hunting for this date in superb gem brilliant PCGS-MS67 grade, at most I recall seeing just one or two blazing white PCGS-MS67 examples. Finally, be on the lookout for the "Type B reverse" of this date as finding one already in a MS66 graded PCGS holder would be a fabulous "cherrypick"! And, if you locate a Type B reverse of this date graded PCGS-MS67, you might just be able to plan a "first class" trip to Las Vegas with all of the profits! The best Type B grade of this date I have been able to find thus far for my personal collection is a PCGS-MS66+ specimen and that took me (25) years to do!