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It's a Truncated Sphere D4 without faces! Have a look to a newer version here.
The idea of keeping only the round part of a truncated sphere die when the numbers are located on vertices or edges is from Clsn (check his D9 for instance).
The thickness is 2 mm and the diameter 25mm (a smaller version for Gold Plated Brass is now also available). Since it does not contain a lot of material, this die is quite affordable.