Here's a side-by-side comparison of the "Ambassador" bead, real Venetian (photo with 2 beads showing different wear) vs. reproduction (from one of the ebay auctions mentioned above). Note that the yellow and red colors differ. The Venetians used a very mustard-y yellow which I believe was derived from sulfur compounds and just not seen in new beads. Note also that the yellow "stems" differ in execution.
I will do the Lewis & Clark bead comparison tomorrow.