B58-060 TRY SQUARE ACCESSORY. Prescott Patent. Patented 7/3/1883 by Edwin Prescott of Arlington, MA, and manufactured by Stanley as an attachment to its squares to enable the user to draw angles. This one is attached to what looks like a 9" Stanley No. 20 try square, marked only with the patent date, user initials punched into handle and blade, handle worn but intact. Rare. Good+ 150-250