Set of 3 Locomotive Progress Train History Books circa 1920-1930s

Set of 3 good, vintage, softcover staplebound booklets; each book is clean, tight, square, and -- but for a prior owner's blacked out address label on the inside front cover of each volume (see photo) -- free of any markings showing lightly thumbed, lightly age-toned pages but only light additional wear; each book cover (wrap) shows light to moderate shelf and corner wear as well as age-toning but remains in good condition; each booklet well illustrated in black and white and published 1927-1930 by the Superheater Company.