Everybody at some point or another has played with, or played against somebody with those goofy looking dice with a club symbol or something else engraved on a facing in lieu of the traditional 6 pips.
When watching those dice roll, you likely noticed how they wobble and just roll funny.
Precision dice are made by drilling out the pips, and then the pips are filled with a paint that is the same weight and density as the original material, thus making them as close to perfect as reasonably possible.
The issue with dice with symbols is they are non-precision dice (which already have a bias towards rolling sixes) with an even larger bias towards rolling 6’s.
When a symbol is used on the 6 side of a die in lieu of pips, a lot more of the original material is cut away. This means that the 1 side is far more likely to end up facing down since it is far heavier. This trait is accentuated by the fact that 90% of dice with a symbol have rounded edges, thus making it easier for the “one” to end up down when rolled.
