Japanese Mystery Egg

My neighbor gave my daughter this "egg" yesterday. She has no idea how she acquired it or how long she has had it. It definitely has some age to it and the only marking is a small raised JAPAN stamp on the bottom. It is incredibly detailed and beautiful with hundreds of real freshwater pearls inside and out. I was thinking it may have been a higher end tourist trinket in maybe the 1950's but that is just a total guess. I have googled every description of this "egg" I can think of and not found ANYTHING like it.
If anyone has any idea of date or history I would love to know! Thanks!