1959, "Steam's Finest Hour" edited by David P. Morgan, Kalmbach Publishing Co., referring to the R-1 Mountain class loco. These 4-8-2's, of which B&M eventually purchased 18 in various subclasses, could almost haul the tonnage of a T and more than made up for the slight deficiency by raising the maximum speed limit from 45 to 70 miles per hour, thanks to 73-inch drivers.
Source: wiktionary