My all-time favorite was "First Century Islamic" beads, by a history-challenged seller - they were actually Venetian if I recall correctly.

Another beauty was "pre-contact" South American beads that were also clearly Venetian. I could not get the seller to explain how European beads arrived in the new world BEFORE anyone from Europe got there!

And I occasionally see phenolic resin beads "from the 19th century" when the first production of this material was 1910.