LIEUTENANT COLONEL DAVID MASON’S GUNNER’S PERPENDICULAR AND Situation, C. 1776 A gunner’s perpendicular, maybe built in Massachusetts. : LIEUTENANT COLONEL DAVID MASON'S GUNNER'S PERPENDICULAR AND Circumstance, C. 1776 A gunner's perpendicular, quite possibly built in Massachusetts, dating for the 2nd 50 % on the 18th century, engraved about