Looks like a P for 1963. In 1963 the Fox Model B listed for $105.50. Savage moved from Chicopee Falls to Westfield between the 1960 and 1961 Savage catalogs. In Chicopee Falls the Model B had a slim forearm and the Model BST had a beavertail forearm. Beginning in 1961 the catalog text for both state beavertail forearm but Savage didn't change the catalog picture until 1966 when they went to impressed checkering.