Here is a LONG list of diesel locomotive classifications:
BBC - Brown Boveri Company, now ABB, Switzerland
BLH - Baldwin-Lima-Hamilton Corporation
BLW - Baldwin Locomotive Works
Budd - Budd Company
EMC - Electro Motive Corporation
EMD - Electro Motive Division
EMD - Electro Motive Diesel
F-M - Fairbanks-Morse
GE - General Electric
GM - General Motors
IS - Ingalls Shipbuilding Company
KM - Krauss-Maffei Aktiengesellschaft, Germany
L-H - Lima-Hamilton
MLW - Montreal Locomotive Works
RailPower - RailPower Technologies Corporation
SIG - Schweizerische Industrie Gesellschaft, Switzerland
UA - United Aircraft, Surface Transportation System of Sikorsky Aircraft Division
WS - Werkspoor N.V. Amsterdam, Netherlands
A unit - Cab Unit
AA - Motorcar A-unit
AB - Motorcar B-unit
AC - Alternating Current
AMD - Amtrak Diesel
AS - ?
B - 2-axles
B unit - Cabless Booster Unit
BL - Branch Line
C - Century (Alco)
C - 3-axles (GE)
C - Cummins (EMD)
CFA - Cab unit Freight A-unit
CFB - Cabless unit Freight B-unit
CPA - Cab unit Passenger A-unit
CPB - Cabless unit Passenger B-unit
DD35B - 8-axles (D-D) using SD35 components B-unit
DDA40X - 8-axles (D-D) A-unit using SD40 components
DL - Dual Service
DR - Diesel Road unit
DRS - Diesel Road Switcher
DRS6-4-15 - 6-axles 4 powered 1,500 Horsepower
DS - Diesel Switcher
DT - Diesel Transfer
E - Eighteen-Hundred Horsepower
Erie - Built at the plant in Erie, PA (F-M)
F - Freight
FL - Freight with special third rail electric pick-up
FP - Freight-Passenger
FT - Freight Twenty-seven-Hundred Horsepower
GP - General Purpose
H - Hood unit
H10-44 - Hood unit, Thousand Horsepower 4-axles 4 powered
HH - High Hood
I - Insulated Cab
LTW - Lightweight Train
M - Montreal-designed
M - North America Wide Cab, DC current
MAC - North America Wide Cab, AC current
MP - Multipurpose
NC - Nine-Hundred Horsepower, Cast Frame
NW - Nine-Hundred Horsepower, Welded Frame
PH - Elongated Frame, Steam Generator
RAm - Locomotive with speed over 110 km/h (R), train composition with 1. class coach (A), diesel engine (m)
RDC - Rail Diesel Car
RF16 - Road Freight 1,600 Horsepower
RS - Road Switcher
RSC - Road Switcher 6-axle, 4 powered (A1A)
RSD - Road Switcher 6-axles
S - Switcher
SC - Six-Hundred Horsepower, Cast Frame
SD - Special Duty
SDP - Special Duty Passenger
SW - Six-Hundred Horsepower, Welded Frame
SW - Switcher (after HP increased over 600 HP)
SW1 - Switcher Version 1
SW900 - Switcher 900 Horsepower
TR - Transfer
U - Universal
VO - ?
W - Wide Cab
And I am sure there are many many many more........
Diesel Locomotive Builders
ALCO - America Locomotive Company BBC - Brown Boveri Company, now ABB, Switzerland
BLH - Baldwin-Lima-Hamilton Corporation
BLW - Baldwin Locomotive Works
Budd - Budd Company
EMC - Electro Motive Corporation
EMD - Electro Motive Division
EMD - Electro Motive Diesel
F-M - Fairbanks-Morse
GE - General Electric
GM - General Motors
IS - Ingalls Shipbuilding Company
KM - Krauss-Maffei Aktiengesellschaft, Germany
L-H - Lima-Hamilton
MLW - Montreal Locomotive Works
RailPower - RailPower Technologies Corporation
SIG - Schweizerische Industrie Gesellschaft, Switzerland
UA - United Aircraft, Surface Transportation System of Sikorsky Aircraft Division
WS - Werkspoor N.V. Amsterdam, Netherlands
Model Classification
4S - 4-axles Switcher A unit - Cab Unit
AA - Motorcar A-unit
AB - Motorcar B-unit
AC - Alternating Current
AMD - Amtrak Diesel
AS - ?
B - 2-axles
B unit - Cabless Booster Unit
BL - Branch Line
C - Century (Alco)
C - 3-axles (GE)
C - Cummins (EMD)
CFA - Cab unit Freight A-unit
CFB - Cabless unit Freight B-unit
CPA - Cab unit Passenger A-unit
CPB - Cabless unit Passenger B-unit
DD35B - 8-axles (D-D) using SD35 components B-unit
DDA40X - 8-axles (D-D) A-unit using SD40 components
DL - Dual Service
DR - Diesel Road unit
DRS - Diesel Road Switcher
DRS6-4-15 - 6-axles 4 powered 1,500 Horsepower
DS - Diesel Switcher
DT - Diesel Transfer
E - Eighteen-Hundred Horsepower
Erie - Built at the plant in Erie, PA (F-M)
F - Freight
FL - Freight with special third rail electric pick-up
FP - Freight-Passenger
FT - Freight Twenty-seven-Hundred Horsepower
GP - General Purpose
H - Hood unit
H10-44 - Hood unit, Thousand Horsepower 4-axles 4 powered
HH - High Hood
I - Insulated Cab
LTW - Lightweight Train
M - Montreal-designed
M - North America Wide Cab, DC current
MAC - North America Wide Cab, AC current
MP - Multipurpose
NC - Nine-Hundred Horsepower, Cast Frame
NW - Nine-Hundred Horsepower, Welded Frame
PH - Elongated Frame, Steam Generator
RAm - Locomotive with speed over 110 km/h (R), train composition with 1. class coach (A), diesel engine (m)
RDC - Rail Diesel Car
RF16 - Road Freight 1,600 Horsepower
RS - Road Switcher
RSC - Road Switcher 6-axle, 4 powered (A1A)
RSD - Road Switcher 6-axles
S - Switcher
SC - Six-Hundred Horsepower, Cast Frame
SD - Special Duty
SDP - Special Duty Passenger
SW - Six-Hundred Horsepower, Welded Frame
SW - Switcher (after HP increased over 600 HP)
SW1 - Switcher Version 1
SW900 - Switcher 900 Horsepower
TR - Transfer
U - Universal
VO - ?
W - Wide Cab
And I am sure there are many many many more........