In the attic looking over the Rirarossi American’s, 4-4-0 Reno and Genoa kits and ready to run locomotives from the early 1960’s .
By using their 1/29 scale pattern models, Riverossi offered many of their trains in HO scale, O scale, N scale (as Atlas) and 1/29 scale (as aristocraft).
These O scale kits were fun to build and very popular in the 1960’s when plastic modeling was the new American pastime. The kits could be built as a shelf model OR motorized to run on a 2 rail DC O gauge model railroad. And they were available “ready to run”. Just sit on your track and go.
These “O” scale models were actually built to 1:43.5 scale. In Europe O scale was 1:45 scale, making the 1.75 inch 0 gauge track true 4 feet 8 1/2 inch standard gauge. In the US most O scale models were 1;48 scale making the gauge 5 feet. Some modeled in “Proto 48” narrowing the gauge but keeping the 1:48 scale. Rivarossi (AHM) opted to go with the European system of modeling to a larger scale. In this case, a bit larger than the 1:45 scale but simpler for their system of making a 1:29 scale pattern model and then reducing it to N, HO, O and 1:29 scale.