the holes are about 3mm, they are rounded inward on one end and flush with the surface or slightly protruding on the other end if that makes sense...

i have some very similar beads- in the 1980s craftsmen/potters experimented making things by hand with porcelain clay using body colours rather than glazing, so they combined layers of colours to give this marbled effect, and made small pottery items and beads.
maybe the only reason it died out was because around then Fimo appeared- and didn't need high temperature firing.
your beads could have been made almost anywhere where there was revived interest in hand crafts at that time- UK, USA, etc.

This is relevant only for background information, I'm sure, but there were marbles made like this in the latter part of the 19th century. Most were white-based layered with a medium blue, some were white-based with a medium green, and others were white-based with both blue and green, alternating. Rarely, one of those will also have thin lines of pink.

They seem to have been made mostly in Germany, although there are a few rare ones that are a little older, apparently from Holland, that are white or cream with brown.

Not a very good pic and not the best examples, but the best I can do on short notice (from ebay) --

Another deleted double post . . . (not a good day for me, apparently . . .)

Erased double post.

Thanks very much for your time and info Stefany and Ann, they're pretty beads even if they're not '19th century Japanese'...makes you wonder where people come up with their misinformation! Wishful thinking perhaps.