The real and fake check is a mythos to serve the big prices arround the scene!
The 'big prices' were only around
until the 'fake' copies showed up. Then people started to pay and buy less because of all the crooked sellers offering bootlegs as 'real'.
Even if you
really do have a legitimate copy, no one will buy it from you now outside of a secure refundable transaction like eBay + PayPal, since you've already called the
very real bootlegs a myth.
In other words, you can't vouch for its authenticity since you're ignorant to the counterfeits in the first place.
But if it
is real, why not sell it for $400 on eBay instead?