In 1910 there was a significant coin shortage of Lincoln cents for circulation. As a result, that same year Banks all over the country were requesting the Treasury Department to send them more cents. Despite having a large mintage of over 146 million, it still was'nt enough to satisfy the demand.
The 1910-P Lincoln cent is not a key date by any means, however it is hard to find raw in grades of 64 and higher. Most examples in MS65 have now been certified and accounted for. Examples in MS66 become scarce with possibly no more than 250 examples available in this grade or higher. In MS67, it is the ultimate grade as there are about 20 examples known with none being finer.