Not disagreeing entirely, just also playing devil's advocate.

 

LTT was the most powerful channeler of his age. He would not have needed to wear the Ring in order to be impressively strong in the Power. He might not have worn it at all except on ceremonial occasions, ala royalty and crowns.

 

Kamarile Maradim Nindar was an ascetic. She probably wouldn't have had much contact with other Aes Sedai. She almost certainly didn't attend anything even hinting of ceremony or pomp and circumstance. Once she became Graendal, she would have had no contact with LTT. In either persona, she may never have seen the Ring.

 

The ring Graendal found has nothing in particular to distinguish it other than that it is small and that she was surprised to find something attuned to a woman among Sam's stuff. Something impressively powerful does not have to be impressive looking, or even uniquely distinguishable.

 

I do agree that the possibility that the ring she found is THE Ring, is very slight.

did she try throwing it in a fire?

well if she throws it in a fire and it says Ring of Tamarlyin in fiery oldtogue characters then it is probably the Ring :lol: Seriously though wouldn't it have the black and white disc on it if it were the ring

I think that's a bit too strong of an assumption. It goes with the "every square is a rectangle but not every rectangle is a square" line of reasoning. If the ring had a black and white disc on it, it would be possible to assume that it was the Ring of Tamyrlin or some other powerful artifact, but to assume that the ring would have to have that design on it in order to be the specific ring that we have no description of,seem completely unfounded.