two black colored rosaries

I don't know if there's any special significance for a rosary being black in color (vs. any other color) or not. Both of these are, anyway.

[hope there aren't any Catholic 'rules' I'm also unaware of that prohibit non-Catholics from having rosaries??]

The one on the LH side has got to be the oldest of the two, with its irregularly shaped beads and brass link wires (some a bit 'stretched') holding them all together to a silver appearing medallion and crucifix. I don't know what the beads themselves are made of except that it isn't glass or plastic, maybe something organic like wood or seeds because they nearly look like they have 'grain', plus the way some are slightly chipped at their ends where the wires pass through. It is *not* marked 'Sterling' anywhere though the backside of the crucifix reads "ANNO SANTO 1925" in raised lettering, I don't know whether to think that is its actual age or not. (could be, maybe?)

The other looks to be a good bit newer, while still nicely detailed its beads might be a plastic material with their size uniformity even though there are subtle differences in the texture and color. The link wires and metal medallion and crucifix are all finished 'black' in color as well. "VIRGEN de GUADALUPE" is depicted on its medallion.