The above is only MY opinion of course based on the site advice linked.  It does not assume people knowingly are trying to sell a fake here as it is not so "clearly" obviously as previously mentioned and many variations appear in the listing pics /quality/ware etc as I finally got through them all and compared to the site pics.....
Also weight seems to be a key if the "how to tell site" is correct....I quote "  

"Weight

An uncirculated florin weighs 11.31g and the fake florin weighs 11.10g. Now 0.21g doesn't sound like a lot but you'd be surprised how little weight a coin loses as it wears. We weighed a mid grade (very fine) florin and the weight was 11.27g, so a worn coin with significant detail missing was just 0.04g lighter! Apparently the fake coin is made from something other than silver to show such a large weight difference."

Well that would be difficult online...anyway.....