Artistic die for playing and collection, part of Nucleii Dice Set. You can print it in any material you wish, but I suggest polished brass, polished bronze or precious plated metals. Silver, gold and platinum are very nice too, but quite expensive. If you prefer plastics instead, I suggest frosted detail plastic.
Following zmail137 suggestion I've done a 25% bigger version, you can find it here: https://www.shapeways.com/product/88D4XEWJL/nucleus-d20-xl
You can find the complete Nucleii Dice Set here: https://www.shapeways.com/product/KN65TZ6J3/nucleii-dice-set