The Class S2 was a particularly distinctive variant.
New York Central Early Power:Volume II 1831-1916 Hardcover Book Alvin F. Staufer
B&O Power Hardcover Book By Lawrence W. Sagle, Alvin F. Staufer
Pennsy Power Pennsylvania Railroad 1900-1957 By Alvin F Staufer 1962
New York Central's Early Power:Volume II 1831-1916 Hardcover By Alvin F. Staufer
Steam Power Of The New York Central System Vol.1 Hardcover Book Alvin F. Staufer
1st Printing Pennsy Power 1900-1957 By Alvin Staufer Hardcover Red
