[Ron Wood]

The "petals" of a Japanese Imperial mum nearly meet in the middle while this stamp has a large open circle in the center. That coupled with Dwight's correct statement that the Japanese Imperial mum was never applied to ordinary items would rule out any Japanese connection and seem to indicate that this is a private mark (possibly manufacturer?) rather than a national mark. It also does not resemble the Siamese "sunburst". As you said Jerry, a mystery.