I find a sure fire way to tell if you have a 'fake' Trading Pin is to look for two things -
Quality of the paint / enamel applied to the pin designs' front, and the luster of said paint / enamel.
Bootlegs, 'Scrappers' and 'fake' pins of questionable origin all either have paint / enamel that does not quite fill in level with the metal 'lines' of the pins design, and / or are not as shiney and 'finished' looking as a official pin.
Those two aspects are dead giveaways you have a 'fake'.
Official 'Pin Trading' Logos on the backsides mean nothing as those are often faked as well.
The quality of the paint application and smoothness of the surface are the two defining differences that can be seen in person.
Very difficult, next to impossible, to see via a photo online.
Official pins have a very full application of enamel /paint so there is rarely gaps or areas where it looks like the amount of paint is not flushed smooth with the metal design and edges of the pin.
Official pins also look buffed and the paint /enamel looks very smooth and shiny on the front surface.
'Fakes' typically lack these features, exspecially the smooth look on the surface.
Most I have come across have a rough looking surface when tilted in the light, thin grading lines being a common feature.
Compare one to a Official one and you will see the difference in the luster / shiny surface factor.
They are easy to spot when you look for these two things!
Happy Trading..!
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