The Origin of the d10
The oldest reference to the d10 we have been able to find is a 1906 US patent. There was no d10 in the original Dungeons & Dragons game in 1974. In fact, at GenCon in 1980 the d10 was first introduced to the gaming industry (and claimed to have been invented).
d10 and D&D
Today, d10s are used extensively in Dungeons and Dragons. Primarily, they are used to determine damage from certain weapons and spells. A d10 can also be used in conjunction with another d10 to make what is known as percentile rolls. Percentile roles determine allow you to roll everything from a 1 to a 100.