Eckhard Boettcher offered several versions of this sort of “Dice Box” over the years, I recall a hexagonal model manufactured by Thomas Pohle, several others from unknown manufacturer.
Later Gert Hoffmann thru his company Magic Design offered this high end polymer model that stunned even those who knew how the trick generally worked. Precision turned by an expert craftsman.
The + was introduced for the special design of the lid which deters from the previously know methods…it simply must work differently…or does it?
This can be used to force numbers or strong prediction effects by Eckhard Boettcher and Jochen Zmeck.
I will include the original German instructions as well as detailed English instructions.