U.S. Model of 1917 rifle, a .30-06 version of the British P-14 that was designed (in .303British) to replace the SMLE. The British had P-14s made in the U.S.A. because their own factories were going flat out to equip their rapidly expanding army in WWI. Soon the whole thing had blown up so large they realised switching rifles was unfeasible until after the war and P-14s were only issued to limited roles. When the Americans joined in and they had to raise an Expeditionary Force for Europe faster than their existing capacity to produce their Springfield service rifle it was faster and cheaper to re-work the P-14 design to .30-06 and use the P-14 factories than to expand the production of Springfield rifles.
So as bearhunter said above, it isn't rare. The U.S.A. troops in Europe for WWI used M1917s much more than they used Springfields. Most M1917s would have been sold off surplus after the war and probably most were converted for sporting use.
Sometimes they are called "the American Enfield" and sometimes the P-17. Some people will say P-17 isn't correct, but while Model of 1917 is more correct because all made in .30-06 were made under that designation, the U.S.A. supplied some to Canada and the U.K. which did give them the designation P-17 because they weren't P-14s.
