touchstone

noun

1. A stone used to verify the quality of gold alloys by rubbing them in order to leave a visible trace.
2. (broadly, figuratively)A standard of comparison or evaluation.

   “Near-synonym: comparator”

   “The foregoing doctrine affords us also a touchstone for the trial of spirits.”

   “"Expectation of life" is an elastic term: the touchstone here is rather the aggregate amount of work that the locomotive does during its working life.”

   “Although there has not been very much direct treatment of the Holocaust in analytic moral philosophy, the Nazis appear again and again as examples or touchstones in the construction of moral theories.”

   “In the print firestorm that followed the publication of the royal couple's letters, the generalissima was one polemical touchstone. The Annotations to The Kings Cabinet Opened itself depicted the queen as an enemy to king and country: […]”

name

1. A surname.