Japanese 5-Lobed Bowl, Un-Marked: What Can Y'all Tell Me About It?

This came into my family in the late 1940's, a gift to Mom from uncle Leonard, a USAAF M/SGT stationed in Nagoya. ~7 3/8" rim diameter, ~2 1/2" height, ~3 1/8 foot-rim diameter; weight 14.5 oz; it is not translucent, but rings like crystal when tapped with a fingernail.

It sat on a south-facing SoCal windowsill for ~30 years, an' I believe the colors suffered some amount of fading as a result.

I would very much appreciate your help identifying where it was produced, an' when...as well as any comments about the symbols on the interior and exterior. As always, Thanks for lookin'!