"" (, "warship roll") is a special type of "nigirizushi": an oval, hand-formed clump of sushi rice that has a strip of "nori" wrapped around its perimeter to form a vessel that is filled with some soft, loose or fine-chopped ingredient that requires the confinement of "nori" such as roe, "nattō", oysters, "uni" (sea urchin roe), corn with mayonnaise, scallops, and quail eggs. "Gunkan-maki" was invented at the "Ginza Kyubey" restaurant in 1941; its invention significantly expanded the repertoire of soft toppings used in sushi.