The holes for stringing are to small. Beads traded with the Indians during the fur trade were usually strung on heavier cordage.
That said, it isn't the only way to judge if beads are old trade beads, but it's part of the process, and is a good indication. I've been told that some Chinese beads had small holes, and the Chinese were somewhat involved in the fur trade, especially for sea otter furs from the Pacific N. West.