I think they're great, Joep, and given the look of them and the fact that they have been making marbles in the Netherlands for a very long time, my bet is they are quite old. How big are they?
Yeah, that's a great marble - they don't come much cleaner!
Nice group, Dave - lots of pink. It reminds me of a big collection I purchased from a woman around here who had collected for a long time - lots of pink and pastel colors on both hand-mades and machine-mades.
Pretty funny story, but since the interior looks threaded, I doubt it was a valve - some kid probably just stuck it in the fitting who knows when. It's definitely a cool Rainbo though, I think I'd be kinda glad for the mishap!
I have about 2 pints of marbles that are still covered in dirt and I am very proud of the discipline I have shown to leave them as they are. Please, don't tempt me! lol
The left is JABO and I think the right one is too. Sometimes marbles can get "furrows" in them because of the way the glass cools or the way the glob moves on the rollers.