77/1781 [Calculators]. Thales calculator, metal and brass(?), ±1900, 24x12x11 cm., on orig. wooden base and with orig. wooden cover w. brass handle and brass lock.

- Key to lock lacking. Otherwise apparently in working order. Some wear/ chipping to the wooden base.

= With the original seller's metal name tag "Adr. Koller & van Os Rotterdam - Amsterdam - Den Haag".