Hi Penguin master,
I can think of several reasons why people don't tend to fake Esties but basically it isn't worth anyones while, good everyday workhorses and as goodlooking as they are in many peoples eyes they aren't worth enough
Concocting a Frankenpen is one thing, these can happen from circumstances over the years and in a way be as genuine as any other pen, the jewel has gone from a schoolboy's working pen (not very likely on most Esties) it looks bad and there is another different model pen in the drawer so the jewel from that ends up in the boy's Estie or a lost cap replaced with one from a different year or whatever
Making a batch of deliberate fakes is quite another thing, Esties as a rule do not fetch big bucks and making pens is not cheap, finding suitable materials like Icicle plastic is next to impossible, setting up for injection moulding, machining or metall stamping isn't cheap either to make it worth while one would have to go for a big run and then the scarce pen is no longer scarce and the fraud is obvious
It would take an encyclopaedic knowledge of the brand to know what to try and fake, if someone knew that much about the brand they would make more by buying and selling genuine rare or scarce pens and wouldn't need too indulge in skullduggery.
People like Gerry and Brian who come across oddballs from people like the 'Benz Collection's' barker tend to let those collectors that frequent places like here and the other pen sites know about them, for example the 'rare colour' Estie that showed up a while ago on offer from the 'Benz Collection' was being discussed and debunked in a matter of a couple of hours after the listing appeared.
On top of all those reasons is the fact that Esties don't have the greed and posing factor of other pens that do get faked, the name of the most faked escapes me for diplomacy's sake

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Sorry for the long post,
cheers, John