It's easy to build a set of 3CS from 1851 through 1862 including the 1851O. Even up to MS63. It just takes a little time to pick nice ones for the grade you are looking for. The years 1863 to 1872 or 1873 are tough and involve compromises. I have a PF50 that I took instead of my target grade of XF40-XF45. Etc.
I have been collecting 3cs for the last 6 years. I have every year in business strike in PCGS or NGC slabs 40-63 EXCEPT the 1868. I talked with the person that won a 1868 in a PCGS AU58 slab a few years ago. He is building a PCGS Everyman registry set and was in competition with other bidders to get that coin. I think it is crazy that the AU55-58 coins are selling for more than the MS60-61 coins but it all about supply and demand.