Gang,
Just an update-- These Crafty (N-square) water pump pliers (catalog number 4492) were available from 1946-1948. Prior to 1946 and after 1948 the water pump pliers were a slip-joint design.
Little is known about the N-square mark; the OEM is unknown, and only three types of tools have been identified that have this mark (pliers, chisels, & punches). This mark has been found on Dunlap branded tools in addition to Craftsman branded tools.