1937-8 Diesels were making their presence known on the American railroads and also in model trains.
Strombecker introduced an HO size wood / cardboard Rocket set in 1937.
1938 Bill Lenoir designed a GMC switcher for Hawk in O gauge and Bill Walther's introduced an Alco switcher for his new HO line .
Alco switcher made use of the same power truck used for the Walthers Doodlebug..and as a power unit for the Strombecker Rocket.
Alco switcher had a heavy (thick) bronze body to be soldered together by the lucky owner ...by 1941 bronze was replaced by white metal and bodies were assembled by the factory .
The Tinplate world would have to wait till the end of the 1940's before having a diesel engine .
Please see link for video of little Alco in action .