The Amusement Park Set
After WWII the 10 1/2 Train Set was not produced. When the Merry-Go-Round model was designed the 9 1/2 Automotive Set got it and became the 10 1/2 Amusement Park set. When production of the larger set resumed about 1948 it became the 12 1/2 Walking Man set.
I built these models with parts from all the sets I had at the time, which is not a good plan. It is better to build each model from one set only so that parts do not get mixed up. In the foreground is the Airplane Ride which the 6 1/2 set with electric motor, or the 4 1/2 with mechanical wind-up motor would build. Left middle is the Merry-Go-Round which the 10 1/2 set would build. Right middle is the Ferris Wheel which the 8 1/2 set would build. And in the back is the Parachute Jump which the 10 1/2 set would build, but I built it with a 12 1/2 set. Another model which the 10 1/2 set would build was the giant power plant, needed to (pretend) power the amusement park rides. Thus, to build a complete amusement park you would need 6 1/2, 8 1/2, two or three 10 1/2, and a 12 1/2 if you only had two 10 1/2. Note: the 9 1/2 from late 1940's would build the parachute jump or the giant power plant, but not the Merry-go-Round. Thus there are several ways to pick the fives sets needed to build the amusement park. And there are other models that you might add to your park.
Here is a picture of the power plant, also called the giant refrigeration plant. There were several versions of this model.
Here are many models built with dozen or more sets that I had at the time, about 1990.