1) Your beads are typical pre-Columbian green-stone beads from México;

2) They are seldom reproduced in a manner that would be compelling, because they are plentiful;

3) There are modern (1970s/80s) serpentine beads, made in Guerrero that were inspired by pre-Columbian beads—but they are visually distinctive and easy to spot.

I have to disagree with Si, regarding the statment that "Modern artifact manufacturers were very skilled...." The fact is the original beads were crude—and did not require 'great skill.' it would be relatively easy to reproduce such beads if there were a need. And there are some reproductions (to be sure). But the common green-stone beads from México were plentiful well-into the 1990s. I don't have an opinion about now. I do however, have some recent reproductions from Guatemala that I think are quite cunning—that I bought in Tucson three years ago.