View of a Mack combustion-engine railbus at Burnham Shops, Denver Colorado, with passengers and porters; a brick building with brackets, bargeboard, and chimneys is in the background.Beam, George L. [1926]. DPL Western History Collection GB-8100

Mack RailBus on trial at D and RGW Burnham Shops. Courtesy DPL Western History Collection GB-8100