Breen wrote about the 1856 Slanted 5 Large Cent Proofs as "...the least rare large cent proofs; over 100 survive." However, the PCGS Population Report shows it as the second most common Large Cent Proof, after the 1857 Small Date. All known examples are of the Newcomb 5 variety which, coincidentally, happens to be a proof-only variety.
The majority of the certified examples are in fine condition, ranging from a low of PR63 to a high of PR66. Red-Brown examples make up the bulk of the surviving population, indicating a high degree of care in their preservation. Full Red Proofs are extremely rare. Finding examples that are free of carbon spots is difficult, but not impossible.
Simpson Collection - Legend-Morphy 5/2014:173 (as part of a complete 1856 Proof Set)
Newcomb 5. Henry Hines - Homer K. Downing - 1952 ANA Sale:2221, $67.50 - John Jay Pittman - David Akers 10/1997:278, $6,050