uphoosier, so many companies did clamshells that I don't think anyone tries to attribute them once they lose their labels. They look so similar to each other. We would have to find one with the same decor to be able to tell who might have made it. Clamshell bowls are very difficult.
Does your bowl have a base that is not part of the main bowl itself? It looks like it is setting on something in the picture. Now THAT would be different.