Inscribedon the front of 2 rules: (on the left) DO NOT FORCE / DIAL BEYOND ZERO LINE (on the right side) MICRO-RULE / PAT. NO. 2554099
on the back of 2 rules: THEO. ALTENEDER & SONS PHILA. PA. / STAINLESS STEEL
on the 2 bolts of the 2 cases: NIELSEN / HARTFORD
FunctionThe micro-rule allows for measurements of greater precision than a traditional marked ruler thanks to an internal mechanism and dial.
ProvenanceLionel Spiro, Brookline, MA; Gift to CHSI, 2014.