A Truncated Sphere die with 50 faces.
This is a Truncated Sphere D50 based on a special polyhedron that is the intersection of a cube (6 squares), an octahedron (8 hexagons with a 3-fold symmetry), a rhombic dodecahdron (12 hexagons with a 2-fold symmetry) and a non-usual icositetrahedron (24 hexagons with a simple symmetry). You can check: 6 + 8 + 12 + 24 = 50.
This model has been made a long time ago (August 2011), but has become public only in December 2013. The reason is that the numbering has been carefully studied to ensure a maximum fairness, and I wanted to challenge anybody to find a better numbering. But now, so much time has passed that I even do not remember the peculiarities of my own numbering. So enjoy it as it is!
Warning: opposite faces do not sum to 51. Actually 1 and 50 are neighbors (see picture). Instead the difference between opposite faces is always 25.