I believe most of the alphabet gauges like S, G, O, HO were made by manufactures in the model train industry.
If 1/48 is marked on box of a plastic model company product it is saying the model picture depicting it is a 1/48 =1' model.
A set of blueprints mary read. drawing is in 1/48 =1'
Another example. The Titanic. Titanic models were mostly done in 1/8 =110' the main model used in the movie came out to be roughly 44' long or 881' in real life. I think that is right, maybe a little off I am in to the third beer.