The 1955-D Lincoln cent is very difficult to find in MS66 grade or higher. Most MS66 examples are average for the grade as this issue has lots of corrosion spots, nicks and scratches and usually just misses the MS66 grade or higher. Few examples that are in MS66 condition are very nice for the grade and any example that is a high end MS66 is a steal if it can be purchased for a regular MS66 price.
In MS67 they are almost unheard of. Even with several of them being graded in MS67 most of the examples just made it for the grade. One of the tougher dates from the 1950's.