No sincere does mean with out wax.. in alchemey, a precursor to real chemisty, to really turn lead into gold, was to be sincere.

And to be insincere was to use a small gold ball, wrapped in wax, and coated with lead dust.

a ball like that could be tossed into a fire, and "emerge" as gold.. that was a charlatan trick. sincere -- with out wax, was true alchemy!(an oxymoron!)