The Canadian Maple Leafs with a bit of 99.99% silver wire through a hole drilled near the top using the silver wire to run up to the lid and have 85% of the coin under the DW(Distilled Water). Somewhere between 5mA and 10mA will be good current for the coin. Look up faradays calculator for how much time, volume in beaker & current to figure out ppm. You can use a copper cathode or stainless steel cause all the metal comes from the anode.