Union Pacific freight cars are refered to by a "Common Standard" system of letters and numbers.
This code is in the form of AA-BB-CC and is
usually painted near the bottom of the car side
AA is one or two letters to designate type of car,
BB is a set of numbers that identify the approximate capacity in
tons,
and CC the series of the car design
So B-50-17 would indicate a boxcar of 50 ton capacity from the
17th series of 50-ton boxcars.
Types include:
B - boxcar
BI - insulated boxcar
BF - flush-door (plug door) boxcar
BC - combination door boxcar (sliding and plug doors)
A - automobile boxcar
CH - covered hopper
H - hopper
HK - ballast hopper (formerly class "BA")
G - gondola
Ore - ore jennies
F- flat car
FD - depressed center flat car
O - tank car ("oil")
CA - caboose (note: car series only, no capacity rating)