I agree with "The precision of the pattern would have been very difficult to achieve in a marble pre-dating the time when most of the handmade German marbles were made 100+ years ago." I don't believe it would have been made in Germany during the time frame of the old Germans, or before. I don't know where else was making glass marbles then. Generally they were being made of agate.
Regardless of the decoration -- which I just cannot see as old (1800s) -- I wouldn't call it a marble. Sphere, orb, something of that nature, maybe. But then I don't call anything over 1 1/4" a marble anyway. Too big to play with.
And just a note: To some of us ancients, 35 years isn't that long ago! Modern glass artists started making marbles (and orbs and spheres) at least 20 years before that! I even have a few of them.
But it certainly is an interesting glass thing, whatever it is, and attractive! The oxblood in the middle is a real puzzler . . .