The rod buffer was the earliest German type of sprung buffer. The first ones consisted of a steel rod that carried the buffer plate at one end. The buffer rod pushed backwards on a spiral volute spring (coil spring), which was supported by a strong sheet metal cylindrical sleeve. Compressing the spring absorbed the impact.
The 1/100 model should have dimensions of 8.4x4x3.7 (two objects that are in the file). Because the model has thin details, a 1/100 printout will be a problem. It is much better to enlarge by 400% and print for 1/25 scale