Here is a picture of some variations seen in the "Lewis & Clark" design Venetian trade bead, compared with a reproduction (listed on ebay in one of the above auctions). Note especially the very thin, rope-like characteristic of the twisted red/white cane on the Venetian bead, which has a lot of variation from bead to bead. As for the Ambassador beads, the red in the Venetian beads has a blue tone, making it more toward a purple color than the orange-y reds seen in newer beads.

I'm sure that it is hard to judge a repro when there is nothing to compare it to, which is one reason to try to handle a lot of beads, as Joyce suggests, before being comfortable purchasing on-line.