The Starrett 14A Double Square is a 2-1/2 in precision square with a hardened steel head and a sliding graduated blade, for layout work and for setting up and checking machinery.
The head and blade are both hardened and ground. The blade is graduated in 32nds and 64ths, etched and black-filled so it's easy to read, and a knurled clamping nut locks it anywhere from full left to full right. Starrett makes it for toolmakers and die makers, and it's small enough for tight spots a larger square won't reach. The 14A comes with the graduated blade only.
Laroy S. Starrett, a Maine farmer's son, patented the combination square in 1879 and founded the L.S. Starrett Company in Athol, Massachusetts, in 1880. Its headquarters and largest plant are still in Athol.