platinum-iridium

platinum-iridium adj.  Standard, against which all others of
   the same category are measured.  Usage: silly.  The notion is that
   one of whatever it is has actually been cast in platinum-iridium
   alloy and placed in the vault beside the Standard Kilogram at the
   International Bureau of Weights and Measures near Paris.  (From
   1889 to 1960, the meter was defined to be the distance between two
   scratches in a platinum-iridium bar kept in that same vault ---
   this replaced an earlier definition as 10^(-7) times the
   distance between the North Pole and the Equator along a meridian
   through Paris; unfortunately, this had been based on an inexact
   value of the circumference of the Earth.  From 1960 to 1984 it was
   defined to be 1650763.73 wavelengths of the orange-red line of
   krypton-86 propagating in a vacuum.  It is now defined as the
   length of the path traveled by light in a vacuum in the time
   interval of 1/299,792,458 of a second.  The kilogram is now the
   only unit of measure officially defined in terms of a unique
   artifact.)  "This garbage-collection algorithm has been tested
   against the platinum-iridium cons cell in Paris."  Compare
   {golden}.