[gap]

Originally Posted by Kendras

How to do that ?

Simple.

1. Select one of the two objects in body selection mode.
2. Switch to face selection mode.
3. Right click on the geometry window.
4. Right click on 'Material' in the following context menu.
5. Enter the new material name.
6. Undo the selection (space bar).
7. Repeat the steps 1-5 for the other copy of the same object, using a different material name.
8. When you have finished, select both objects in body selection mode.
9. Right click on the geometry window.
10. Choose 'Combine' from the context menu.

Done