Hmm, looking in to the signature thing, maybe I was too hasty with the price drop...
This is the original press release from no treble (mine doesn't have a gig bag) : https://www.notreble.com/buzz/2015/01/25/marcus-miller-teams-with-sire-guitars-for-new-signature-basses/
If I remember correctly, the first 1000 of them were signed by MM as a way to drum up interest at launch (this is number 913).
I bought this second hand in 2015 not long after the launch so would assume its legit but have no way to verify this. Its never been a big concern of mine as its a fantastic bass at a superb price no matter who has written on it.
Don't know if any other BCers have info on the signature?
I had a squier 60s cv jazz before this, and ultimately got rid of the squier. I thought the sire plays and sounds better.
Will look into postage and DM you. I would imagine it's cheaper than driving to Glasgow (and I'm sure scot gov will ban us all from travelling by the end of the week).