Right, the Ring of Barahir, given to Barahir by Finrod (I think, memory's a bit hazy), and passed down to Beren and from him through the Numenoreans and finally to Aragorn, but, well how?
When Beren and Luthien finally died a second death, it had been a while since anyone had seen them, so was the ring given to Dior when he went back to Doriath?
I'm sure this is all mentioned in the Silmarillion or Lost Tales or something, but I haven't the mind to go through them looking for such information.
Eventually it will have been something that the Edain took to Numenor and then Elendil and his sons took to Middle Earth, but there just seems to be some bits missing. It's all very neat and tidy.