While I can't comment on the smudged label (could you post a shot of it?), the fact that it works shows it might be genuine. (None of the non-genuine or -licensed display adapters / cables work.)
Furthermore, I haven't ever seen a non-genuine VGA / HDMI adapter, as opposed to composite cables / video adapters. (This, however, doesn't necessarily mean yours isn't genuine.)
Thanks for your reply
I've attached a few pictures below:
Its a little difficult to see on a photo, but the model number part of the printing 'A1388' is near unreadable it is that smudged
The printing of the labels 'HDMI' etc is quite dark coloured whereas the colouring to similar labels on my other cables/adapters is quite light.
And finally, the ports themselves have very dark inner parts whereas any photo of the adapter I've seen on the internet, clearly show the ports have white inner parts.