Silver Rings are ordinary, wearable rings that have no known magical properties. They can be found in a Chest in B2 of Aborek, as well in a couple of other chests deeper inside the dungeon. They are not used in any Enchanting recipes, but can be given to Siomir at the Gem Shop in Lerilin for 50 Experience Points.
Given the low payout of this quest, one might do better by wearing the ring as a fashion statement, or by giving it to collectors. One such collector is the traveling hunter Nal, who will offer 5 Dragon Teeth to anyone willing to part with a Silver Ring. Be warned, though, locating Nal is said to be as difficult as locating Rung.
Like with the other three common rings (gold, crystal, and platinum), Silver Rings could once be found as relatively common loot on certain creatures, and could be sold at the Gem Shop for a very low sum. But this was many years ago, and the proprietors of the Gem Shops do not appear to be interested in buying common rings any longer.