The Bauer BG 6 is a medium sized drilling rig that isn’t in production anymore.
Therefore, the combination of this rig with a rather new Liebherr R 914 that should hardly be found in reality.

With the rotary drilling method, the drilling rig first drills a large diameter steel pipe several feet into the ground an removes the “drillig core” with a auger (or a clamshell when working in soft ground) alternately. When the casing has reached the desired depth, it can be filled with conrete to form a grounding pile for a heavy building for example. When the concrete is filled in, the tube is pulled out of the ground for further re-use.
At the model, the casing oscillator and the auger are clearly visible.
You can read about the assembling of this kit here.