The electrum piece was a type of currency formerly used in the role-playing game Dungeons and Dragons. The bastard step-child of DnD currencies, it was always rare, mostly because in an era before Wikipedia, nobody really knew exactly what electrum was. Thus, although mentioned in the rules it almost never appeared as findable loot in published adventure modules. It was finally, mercifully killed off when the 3rd Edition was published in 2004.
However, it turns out that in the real world, electrum had a long history of use as a major form of currency among the ancient civilizations of Greece and Turkey. A naturally occurring alloy of gold and silver, it was more durable than pure gold or silver and also much easier to refine. However, it eventually fell out of favor because the exact ratio of gold to silver in electrum coins often differed wildly and thus it was an unreliable store of value, susceptible to forgeries composed mostly of silver or other lesser metals.