I've had fake MicroSD cards sent to me previously when bought online - but the attention to detail in the fake BOSE QC35 headphones I recently received was amazing.
After ordering my Bose QuietComfort 35 noise-cancelling headphones off Ebay, I was surprised how slick they looked - but the positive impression did not last. Once I plugged them in and charged them up it became painfully apparent that the electronics inside them were not up to scratch:
1) They would cut out intermittently from the Bluetooth connection.
2) The noise cancellation was ineffective. I've used the QC25 headphones before and it is clear when the noise cancellation is turned on and off (thinking night and day). When noise cancellation is on, it reminds me of when people go deaf (in movies like "Saving Private Ryan" or "Dunkirk") from the concussive effects of a grenade or bomb (yes they're that good!).
I contacted Bose (Report_Counterfeits@bose.com) and they confirmed that they were in fact very well done fakes and they didn't exhibit most of the superficial faults that most fakes have. In particular, the "BOSE" writing on the headphones was embossed perfectly and there was no clear marks where the ear cups had been glued together. All the serial numbers on the headphones and on the box also matched. The box, plastic and packaging was also hard to fault.
The only issue was that the serial number was invalid - the number after the Z is meant to be a date.
S/N:072536Z08231568AE
So it seems that the most important (and most expensive components) - the internal chips and electronics - are the part you are probably paying for and the part that is hardest to reproduce accurately by the guys making the yum-cha/knock-off copies.
So the simplest way to check for a fake is to attempt to register you headphones online at:
https://www.bose.com.au/en_au/support/product_registration.html
The guy I was dealing with on Ebay even tried to negotiate the refund to 30% of the original price before I told him how it is meant to work. Make sure you demand a 100% refund including the return postage cost on a fake substandard item like this. The guys at BOSE will also help you to get a refund if needs be.
Hope this helps!
DDK