These models date back to the early days of N scale (late 60s / early 70s). They had various importers over the years (Revell and Walthers, most noteably).
The boom car was also available with a small hoist instead of that "bobber" caboose body -
I'm told that the prototype for this model is a 75-ton crane of the former German National Railways (note: metric tons, so 75 tons would be about 83 American tons).