it's a round cube with a 13mm metal ball inside
What you need:
1. 12mm-13mm meta ball
2. Glue
Assembly:
1. Place the metal ball in the cube halves marked with the "1"
2. Fill the holes of the cube half "1" with glue
3. Glue both cube halves together
4. Turn the cube so that the "1" is on top
12mm metal ball: https://www.amazon.de/dp/B08WNKCFP8/ref=cm_sw_r_apan_glt_i_A3ZFX0MJTJF9E2TZ8BZ4?psc=1
The author marked this model as their own original creation.