Operating Era: 1913-1953. Pennsylvania RR. Pennsy`s first all-steel house car, it was built on the same underframe as the X23. A demonstrator was built in 1913. Between 1915 and 1919 9,620 of the design were produced. Cars delivered through 1916 had plate steel doors while later cars had corrugated doors. Cars delivered through 1917 were given the Union Line logo. Beginning in the late 1920`s, cars requiring rebuilding were given corrugated doors and door rollers. Both original and modernized cars ran contemporaneously to scrapping in the early 1950`s.