Aristo Aviat 617 air navigation computer / calculator with leather slip case. The computer side with highlighted scales and color tinting distinguish the various scales and a transparent, rotating cursor with index line for setting and reading between graduations. Functions for computations of speed, distance, time, fuel consumption and pressure pattern navigation problems and for determining true air speed, altitude and density, speed of sound and Mach number. The wind side of the device with wind arm and engineered slide with colored lettering, a scale for the usual distance-time speed problems, fuel consumption and wind triangle computations, the Aviat 617 has scales for rapid conversion between British/US and Metric units of measurement, as well as for liquid measures at various specific gravities, to their equivalents in pounds weight or kilos. Special scales or marks are provided for the determination of true air speed, true altitude and density altitude, speed of sound and Mach number, as well as for the solution of problems in pressure pattern navigation. The leather slip case with deteriorated stitching, calculator / computer with