The small silver ring was the ring of truth.
It granted the wearer of the ring a powerful ability, the power to always be correct. Essentially, the ring alters reality itself in order to make any statement by the wearer of any question accurate.
If the wearer were to say, for example, that man's best friend is the cow, then reality would change so that cows would replace dog's as people's faithful companions. Or if the wearer says that the allies lost world war 2, then the wring will make it so that they had lost all along. The ramifications will be anywhere from practically unnoticeable to life changing.
Also, questions are always inverted so that the wearer is wrong. If the wearer asks, for example, his friend if he's free for today, and the answer would be yes, then reality will change so that the friend isn't free. Or if he asks his mother if her favorite how is Breaking bad, and she say isn't a fan at all, then she'll suddenly become the show's biggest fan and reply with a resounding yes.
What's also important is that while the ring alters reality to make the wearer correct, nobody will notice the changes. By that extent, if someone were to wear the ring on their left hand, then they would be unaware of the changes like everyone else. If the wearer puts it on his right finger, however, then they will be able to realize that things are changing.
The ring sat there, magically enchanting as per usual. Whenever it was not worn, it constantly created a small spell which made it appealing, and made those nearby want to try it on.