A rare and fine Tachygraphe (French) or Tachograph in brass complete with dividers and case.
Signed “TACHYGRAPHE, E. de Louvencourt, Inspecteur de Chemins de fer de l’Est”, this instrument consists of a straight edge, hinged parallel rule, scaled vernier caliper/protractor with gradations from 0-100 and a pair of 4″ (10 cm.-small) dividers.
By plotting distances from maps/charts/routes over time and/or speed over time, the variations/deviations of revolutions per minute (RPM) can be calculated using this unique instrument.
Originally proposed and patented by
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