Japanese Ceramic Soup or Rice Bowl

Japanese Ceramic Soup or Rice Bowl-This white ceramic bowl is 7 ¼ inches (18.41cm) in diameter and sits just about 1 ½ inches (3.81cm) deep. It is very shallow. There is a green 5-pointed Japanese star on the side of this bowl. It is marked on the bottom with a maker's mark and the number 28. I have been unable to identify what this means. I'm uncertain what this bowl would be used for, but it looks to be a bit roughly made, I'm thinking for military mess use. Overall, it is in good condition.