Clear and complete stamp of WP #348 寸 'Sun' on a standard Hokkaido roller.
'Sun' (pronounced 'soon') is a measurement. It's a tenth of a shaku or about an inch (3.03 cm). It's also used as a slang term to mean little or small.
Mark WP #348 is classified as uncommon when stamped on small glass balls. Finding this mark stamped on a roller is a bit unusual. I've only seen a few of them.
Found on Hokkaido Island, Japan.