The marbles shown in the article remind me a little of the Svenska Stenkulors but they appear have a final glaze or treatment of some sort. Yours don't look quite as glossy.
Very cool, Fire!
Here's an interesting little article about them. You may need to translate from french. Apparently the company opened in 1998.
https://forum.trictrac.net/t/article-billes-traditions-la-vraie-bille-en-terre/195137
You may be right about a double ingot, but there is usually still some sign of the interface between the two ingots, even if it is all smoothed out.
And I'll have to get into the archives and see what I can find - is a row 5 marbles or 6?
🙂
I get the feeling that your photo is a little bright so it's hard to tell from these pics. But it does have that "mottled" look that you often see on oxblood so . . . ?