Fake A8's have a silver end cap on the "arm" - at least all the ones I've seen so far.
Other diffferences ( apart from crappy sound !! ) are the writing is not printed cleanly, the wires are lower spec, the leather pouch is plastic, and there is noticeably low grade packaging.
As per the earlier post, with any online BeoBargain, if its too good to be true ( and £40 for A8's is too good to be true ) its generally because its a rip off. Or stolen.
Bang & Olufsen of King Street - Manchester,UK.
SKYPE - beokingstreet