Here's a little plaything from Norse legend:
The Ring of the Niflung Horde
This ancient artifact was forged by ethereals of the Norse pantheon, and was taken from the dwarf Andvari by none other than Loki himself. In appearance it is a heavy ring wrought from flame-red gold. If placed upon a finger before going to sleep, in the morning the bearer will find similar rings upon all his fingers. Each of these nine new rings is yellower in color than the original, and thus easily told apart; they have no special properties.
However, the magical ring of wealth carries with it a strong curse. Each night that the wearer sleeps with it on, he must make a willpower check; if he fails, he acquires a level of the Greedy discord, up to level six. This discord may only be gotten rid of by freely giving the ring to another person, a rather unlikely occurrence. Getting rid of the ring without giving it to someone else will only cause the former owner to want it more. Additionally, all who know about the power of the ring and who lay eyes on it must make willpower checks every day they are in its presence. Failure means they acquire a level of Greedy directed specifically at the ring. At the higher levels this will lead to murdering one's own family to possess the cursed wealth-bringer.
Draupnir was a golden armring created for Othin as part of a competition, where two dwarves were trying to produce the best set of gifts. (Thor's hammer Mjolnir also comes from this competition.) Depending on the version of the legend, Draupnir has the magical ability to spawn either nine or eight identical rings either every night or every ninth night. (Nine is of mystical significance, and the original storytellers apparently couldn't decide whether there should be nine new rings or nine rings total.)
Then there's the story told in the poems of the Elder Edda and the Volsungsaga, as well as newer sources such as the medieval Germanic Nibelungenlied and Wagner's Ring Cycle. In it, there's a ring that was originally taken from the dwarf Andvari by Loki to pay for a ransom, and cursed by him, for it was the last of his wealth. According to some versions of the story, Andvari claims that if he had been able to keep the ring, he would have been able to replenish his fortune, and this has sometimes been taken to mean that it had the cloning power, possibly by conflation with the other story about Othin.
With regards to the spelling, Niflung is not a mistake, as it is the original Norse version, written down in Iceland around the 11th century, but dating back to some time around the 6th or 7th century. The potentially more familiar Nibelung is from the medieval Germanic version of the story, which is much duller.
And here's a different take:
The Ring of Frustration
This ring, by all appearances, seems to be identical to the true ring, being made out of the same red gold. However, it is actually of far more recent provenance, probably having been forged by some forgotten trickster god. If worn overnight, in the morning the bearer will find an identical ring on each of his fingers, down to the last detail. None of the new nine rings, though, have any magical properties. However, the original ring will likely have moved to a different finger (it's equally likely to be any of the rings, including the one on the finger it was originally occupying)! The only way to tell the magical ring apart from the ordinary clones is to wear it overnight again and see the new rings it has produced. Compounding the problem, if the magical ring is worn along with any of its offspring, it'll only produce new rings on the fingers that are unoccupied. Any attempt to melt down or otherwise harm the magical ring will destroy it, but it always seems to turn up again somewhere else. Some theorize that this ring was actually made as a means to bring people together in response to the original, which only sowed strife, since the only way to maximize the utility of this ring is to have ten people who trust each other, each of who puts one of the rings from the previous night. It does not engender any sort of supernatural greediness.