Bowker 2-4-0 Steam Engine
Genoa 4-4-0 Steam Engine
Reno 4-4-0 Steam Engine
Casey Jones 4-6-0 Steam Engine
Inyo Steam Engine
Baldwin American Steam Engine
Hudson J3a 4-6-4 Steam Engine
Streamlined Hudson Steam Engine
Big Boy 4-8-8-4 Steam Engine
Northern 4-8-4 Steam Engine
Challenger 4-6-6-4 Steam Engine
Heisler Steam Engine -Two Truck
Heisler Steam Engine -Three Truck
Berkshire 2-8-4 Steam Engine
A-3 Switcher Steam Engine
Mikado 2-8-2 Steam Engine
Smoking "Big Mikes" 2-8-2 Steam Engine
Heavy Pacific 4-6-2 Steam Engine
C&O F-19 Pacific 4-6-2 Steam Engine
Simplified Pacific 4-6-2 Steam Engine
Light Pacific 4-6-2 Steam Engine
Dockside 0-4-0 Steam Engine
Booster 0-4-0 Steam Engine
Saddle Tank 0-6-0 Steam Engine
0-6-0 Steam Engine
USRA 0-6-0 Switcher Steam Engine
Shifter 0-4-0 Steam Engine
Switcher 0-8-0 Steam Engine
"Santa Fe" Class S-1 2-10-2 Steam Engine
USRA Mallet 2-8-8-2 Steam Engine
2-8-8-0 EL-3 Mallet Steam Engine
Santa Fe Blue Goose Steam Engine
Cab Forward 4-8-8-2 Steam Engine
C&O L-2 Hudson Steam Engine
Brass Locomotives
Simulated Gold Locomotives
French Pacific
Trevithick's 1804 Locomotive kit
Kitmaster Kits
ALCO 1000
ALCO Century 424
ALCO Century 420
ALCO Century 628
ALCO RS-2 Powered & Dummy
GE 35 Ton Switcher
GE Center Cab
GG-1 Electric
EMD SW1 w/Brakeman and Light
EMD FP45 -Yugoslovia
EMD FP45C -Lima
EMD GP18 w/Flashing Beacon
FM C-Liner
FM C-Liner B-Unit
Krauss Maffei
Plymouth MDT Switcher
Boeing LRV Trolley
Birney/Brill Trolley

ALCO Century 420
Penn Central 

ALCO Century 420
Santa Fe 

ALCO Century 420
Union Pacific

To date, I have never encountered an AHM HO-scale Century 420. The three road names and stock numbers presented are from a mid-1970s AHM price listing with no pictures.

My guess is this would have possibly been the Lima Century 420 model. Lima's Century 420 did find itself available in the 1970s in the U.S., but it was sold by Model Power/PMI and not AHM. For a time in the 1970s Model Power had a secondary line under the PMI, Precision Models Inc., name and this line included what I believe is the first American release of this Italian-made HO Century 420 offering. The February 1976 issue of Railroad Model Craftsman includes a product review of this model. The PMI roster included the trio of road names promised from AHM (Penn Central, Santa Fe, and Union Pacific) and added a Canadian Pacific release.

By AHM's 1977 catalogs and price listings, there is no mention of this model. As a Model Power/PMI release, the Lima Century 420 was available decorated for Santa Fe, Union Pacific, Penn Central, Canadian Pacific, Spirit of '76, and Chessie.

Lima also sold the model under its own name and it was available here in the U.S. from them. Among that release is an interesting Southern Pacific Daylight experimental scheme.

Similar to its FP45 sold by AHM for a short time, this Century 420 presented swinging pilots attached to the trucks in a Lionel-like design. Lima also produced a high-end Century 420 model that included finer detail and omitted the pilots mounted to the trucks. MRC (Model Rectifier Corp.) originally marketed this enhanced HO Century 420 in the U.S.

You may read more about the history of ALCO at Wikipedia.org.

Image sources include AHM product catalogs and advertisments, as well as images from eBay auctions and other sources. Information presented comes from variety of sources including product catalogs, magazine articles and Wikipedia.