Made in Canada for Ontario Hughes Owens Co. Ltd. Stores reference 6B/108. Circular white metal instrument. Has rotating discs for setting the ground barometric pressure, temperature, indicated height and airspeed. For use with isothermic calibrated altimeters. Used by Navigators when plotting routes etc. Well marked early example. Predates the more commonly found MK.II & IIA. Super condition. Stock code M20431.