This is a good old used 5" spring outside caliper(6.0" long overall). Nice design, in good condition with some darkening to the finish, a few areas have very minor pitting, little wear, some tiny edge dings, the joint is still quite snug, and holds position well. It is clearly marked "STANDARD TOOL CO. ATHOL MASS. THE BOSS ". Standard tool was bought out by Starrett Tool Co. pre-1900. There is very few tools found today with this name on them although many of the patented tools were still manufactured and sold by Starrett well into the 1900's. A rare find!