This is a very rare and interesting Japanese military sake cup, made to be portable and in the shape of an egg with three cups fitting tightly inside the egg. The exterior of the egg has the insignia of the Navy Association, and on the inside rim of the egg holder has the words "Commemoration" "Navy Association Osaka Prefecture Branch". I believe this association was for members or ex-members of the navy but was abolished after the war. The egg's top is a screw on top. I believe the shell is made of aluminium. The interior I'm not so sure.

Condition: There's some dings and scratches on the exterior of the egg. 

Size: The egg is literally the size of about a normal egg