The mold mark is more confusing than the piece

I scooped up this beauty yesterday and thought I'd just be looking for a pattern. Clean up proved otherwise! I realized this little pedestal has an off center mold mark - and I am CLUELESS (pic 3)! Capital R with 2 smaller figures to the right (U? D?), one over the other, THEN 6 digits...285342. Was thia even American made?
Measures 7 1/2" bowl diameter, and about 4" tall
The light sun purpling proves manganese, and it does flouress under UV, I'm just in the dark!