For what I remember from an old article on a European car magazine that was talking about die-cast, the 1/24 was used in Europe and 1/25 in USA.The article were saying that they wanted a specific scale back then for different reason, one was production cost, and selling cost. Also they wanted a scale (1/24) that almost any kid or adult can enjoy. THe 1/24 scale was a big hit in the middle of the 70's when Bburago started to make toys model cars, after adding the 1/43 and 1/18 and kit etc...