Additional types of these cars were developed, all with the same overall length, body shape, and characteristic round end windows often referred to as porthole or owl-eyed windows and large roof-level headlights.Staufer (1993), pp. 496, 504 The passenger-baggage combination cars (52 seats) were designated MPB54. In 1911, baggage cars with baggage compartments were added and designated MB62. In 1913, baggage-mail cars with the same dimensions were added and designated MBM62. In 1914, passenger-baggage combination cars with longer baggage compartments and 40 seats were added and designated MPB54B. In 1915, passenger-baggage-mail combination cars with 24 seats were added and designated MPBM54.
