The 1934-D Lincoln cent is the last date from Denver Mint that is considered scarce in in grades of MS64 Red and higher.
MS60 - MS63 Red: In grades of MS60 to MS63 Red they can be located without much effort.
MS64 Red: In MS64 Red it is still considered scarce but yet it is obtainable with proper searching.
MS65 Red: In MS65 Red grades it becomes difficult to find and most examples are probably low end MS65's as the coins tend to come spotted and with nicks and scratches. There are possibly about 1,500 examples that survive in MS65 Red grade.
MS66 Red: In MS66 Red it is very difficult to find as most coins come with some spotting, weak strikes nicks and scratches or they lack luster, which keeps them from receiving the MS66 grade. There are probably about 400 - 450 coins that grade MS66 Red.
MS67 Red: In MS67 Red it is considered truly scarce, with about 25 coins in this grade and none being higher.