I watched this one recently come and go in at auction as part of the late dealer/collector Matt King's estate, one in a lot of several objects. (With most everything fetching prices  way beyond me, I gave up.). But then this little whimsy showed up elsewhere (I guess the buyer bought the lot for something else in it) so I grabbed it. How that marble got inside is a bit less of a mystery than I thought (one short end shows a diagonal cut, so the wood must have been eased apart and the marble forced inside), but nice paint, and perfectly complementary glass marble, and I love the boxiness of the from and the little peephole at either end through which one sees pure sapphire blue! 

2 3/4" x 1 1/2" x 1 5/8". Good overall antique condition, with general wear. Cut visible on one short end as noted. Surface shows a mix of a darker blue green and lighter blue paint--a bit more pronounced in photos than in hand.