Phil and Rod,

The deGolyer Library at Southern Methodist University in Dallas, Texas, has a large collection of Baldwin information. Taken from their web site:

Example: 10-24 D 35

35 = Indicates the 35th locomotive in the class.

D = 3 pairs of driving wheels

24 = Number representing size of cylinder

10 = Indicates a total of 10 wheels

a. The initial number is the total number of wheels of all kinds under the locomotive

b. The second number indicates the cylinder diameter in inches, this quantity being obtained by dividing the cylinder diameter by 2 and adding 3 to the quotient. The above classification number of 24 indicates a cylinder diameter of (24 รท 2) + 3 = 15".

A fraction, 42/68 indicates a compound locomotive having two cylinders.

A second fraction of 1/2, 1/3 or 1/4 gives the arrangement of the truck wheels.

1/3 designates a trailing truck only, 1/4 designates a leading and trailing truck.

1/2 denoted a locomotive with some special feature such as condensing equipment.

Units with no fraction had only leading trucks.

c. The letter designation indicates the number of pairs of coupled driving wheels.

"A" = special class of high speed geared locomotive with one pair of driving wheels. Also rack railroad locomotives.

"B" = one pair of driving wheels.

"C" = two pairs of coupled driving wheels.

"D" = three pairs of coupled driving wheels.

"E" = f our pairs of coupled driving wheels.

"F" = five pairs of coupled driving wheels.

Double letters = articulated locomotives having more than one set of coupled driving wheels.

Check out their website for the Baldwin Collection:

http://www.lib.utexas.edu/taro/smu/00052/smu-00052.htmlDave Crow