If it says "RailKing Scale", it is a 1:48 model using old Premier tooling that does not meet the detail expectations of the current market. (These are almost all diesels/maybe electrics, and can represent real bargains, even when new. The RK USRA 0-8-0 is a 1:48-sized model with basic detailing.)
Most non-scale RK items - and that is nearly all of them - are not "proportioned"/scaled to any precise ratio, it seems. Some are toy-like, some are better-toy-like and some are very presentable. I always mention the RK Triplex here, which has scale-sized cab, cylinders, pilot, general girth and so on that are found on a shorter machine with smaller drivers - it looks like a 1:48 model of a smaller Triplex. Very nice piece.