The story of this ring begins thus: "A ring owned by King Helgi was a widely famed treasure. Both brothers wanted it, and so too did their sister Signy."
King Hroar offered to give his brother, King Helgi, his share of the kingdom in exchange for the ring, saying, "I want the ring, the one that is the best treasure in your possession and that both of us would like to own." Basically, Hroar saw this ring as worth half a kingdom.
Helgi agreed to this deal, "after such a speech, nothing else is fitting but that you should have the ring."
However, that is not the end of the episode. Hrok, with the encouragement of his mother Signy, also decided he wanted the ring. He demanded that King Helgi (his uncle) give him a third of the kingdom or "the great ring." Helgi informed him that Hroar had the ring and that his claims were arrogant.
|Isildur and The One Ring|
Hrok then asked to see it, saying he wanted to know if it was really "as much a treasure as it is claimed." Hroar readily showed it too him and Hrok threw it into the sea after saying, "I have never seen a comparable treasure, and the reason you esteem the ring so highly is obvious. The best solution, it seems to me, is that neither of us, or, for that matter, anyone else should enjoy it." He had no right to such an action. His claim on the ring was small enough, and Hroar had traded half the kingdom for it. Hroar chopped of Hrok's foot in response. After healing, Hrok assembled an army with which he defeated and killed Hroar. Helgi then defeated Hrok and instead of slaying him, broke all his limbs so that he was a cripple the rest of his life. And this was all between family! Many people searched the waters for the ring and Hroar's son, Agnar, finally found it after diving for it.
So, that's a summary of the ring episode. Although this ring was not imbued with the magical and evil properties that The One Ring possessed, it was coveted in much the same way, resulting in wars and the loss of limbs (Frodo lost his finger, Hrok, his foot). Hrok referred to it as "the great ring," giving it a title, much like, "The One Ring." In The Lord of the Rings, it was suggested the the ring be thrown into the sea, but that idea was rejected because it could be found again eventually.
However, Hroar's ring could have been an arm ring and not a finger ring like The One Ring.
The Saga of Hrolf Kraki. Translated by Jesse L. Bylock. Published by Penguin Books, 1998.