A rare steel machinist's/inspector's Mason Cap Gauge from Ball Bros Glass Mfg Co in Muncie, Indiana. This heavy iron tool is a "GO / NO-GO" gauge for "STANDARD MASON CAPS" and is dated "SEPT - 6 - 1923". The original provenance of this item is from a Mr. Charlie Lawson who was employed as a machinist during that time at the Ball Plant in Muncie. The "GO" end of the gauge is marked "MIN 2.730" and the "NO-GO" end of the gauge is marked "MAX 2.770". Allowing for a size range of 40/1000" of an inch in variation. This would have been used to test their production of zinc caps for acceptable size range compliance. Untouched condition and finely made. Extremely rare.