If you're talking about "silver" post-1816 coins that are actually copper washed with silver, these are actually not fakes but forgeries produced at the time. Collectors know all about these (indeed our own seuk has made an expert study of them), and they should be classed as 'items of interest' and not as counterfeits. And in the US, GIII copper "evasions" from the mid-18th Century are widely collected and valued. If they are actually modern reproductions and sold as such, I don't see that any law has been broken if they are not misrepresented. They may be sold described as modern repros by the manufacturer but, as they don't carry any mark making it clear as to what they are, I suppose problems could arise further down the line? Indeed they could - but that's the responsibility of a future 'rogue trader', not of eBay or an honest seller. After all, bottles of Chanel are sold every day without regard to the Del Boys of this world who will go around collecting up the empties, filling them with cheap scent, and flogging them out of a suitcase on Peckham High Street ("fell off the back of a lorry, John, take it from me..").