"P.S.A.L." NYC probably stands for Public School Athletic League.  NYC once allowed marksmanship competition in the public schools (gasp).  Your rear sight should have small "C" on right side of base.  Ladder increments should go up to 20 (2,000 yards) and have "C" above 19.  Similar looking model 1896 Rifle sight only goes up to 18.  Carbine rear sight is worth about $500 and often switched by profiteers!