Who gets my mother’s wedding ring?

My mother is Japanese and my father is white. I was born and raised in the US. Last year, my mother passed away. So, my father, thinking he was doing the right thing (by Japanese custom), gave the ring to his oldest grand-daughter. However, my sister is very upset and claims a right to the ring, saying that Japanese custom says that the oldest daughter gets the wedding ring, not the oldest grand-daughter. So who is right? Any help is greatly appreciated - we are desperate over here!

There is no particular way which memento goes to which person.
There are always arguments which memento goes to which person especially the item is valuable.

I've never heard of any "Japanese custom" about wedding rings. Wedding rings came from Western culture anyway, most likely in the late 19th century.

So I don't understand why your father thought it was a "Japanese custom" to give the ring to his grand-daughter. Similarly, I don't think the "custom" suggests that your sister has the right.

Anyway, the whole misunderstanding seems to come from this "custom" thing.

Perhaps your mother had told your dad that she wanted the grand-daughter to have the ring, and your dad just assumed it was the custom. Just a wild guess, though. Either way, you should all put this "custom" story aside and figure out how this misunderstanding happened. And THEN you can start talking about who should have the ring.

The following link is just a Japanese language source to back up my post.
http://www.perfumy-online.info/0004.html
http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q1466341944
https://www.google.co.jp/search?sourceid=navclient&aq=&oq=%e6%ad%bb%e3...