The March 2022 Railroad Model Craftsman contains an article, reprinted from their November 1936 issue, on building an OO scale hopper. Which is a neat thing to see.

However, as others have also noted, there is a huge error in the modern side bar added to the article, they describe OO scale models as running on HO gauge track. The PSA today being that American OO models do not run on HO gauge track, they run on proper OO gauge track. Since the beginning of American OO in 1930, it has always been 1/76 scale models running on 19MM (3/4”) gauge track. Models were manufactured in large commercial quantities for this scale and gauge combination by Nason, Scale-Craft, and Lionel (among others), with interest peaking just before WWII.

To see American OO described as it was in the sidebar is disappointing, but not really a surprise. People today often assume it was an American version of HO/OO like the British do, OO scale models running on HO gauge track. But no. The illustration below, from the October, 1939 issue of Miniature Railroading, makes the comparison of scale and gauge very clear. The early advocates of American OO were clear in a desire to match 4MM scale models with a track that was the correct gauge, improving on the early British OO (which is still produced with OO bodies riding on HO gauge track).

This PSA also serves as a reminder for all of us to spread the word on exactly what American OO is. Spread the word! And point people to this site and my book for more information on the topic.