Ford, if you hadn't already seen it, here's a link with some information and a picture of the Marmaduke Guitar:
https://www.bromptons.co/reference/articles/details/sanctus-seraphin-2.htmlYour guitar certainly has a lot in common with it, most obviously the control layout is similar, tailed bird tailpiece, and body contours. I'm thinking the omega cut on his was a little different shape, and it had the 6-inline headstock.
Possibly another clue; there's been a guy trying to sell another mystery guitar with some possible, dare I say probable, Alembic DNA on ebay. While he's a little ambitious in pricing it, the people he's trying to gain some provenance from might also be familiar with your guitar. (read in the item description).
http://pages.ebay.com/link/?nav=item.view&id=282095058442&alt=web The various players in that thread pretty much echo that in those days, not all work was necessarily sanctioned and/or authorized.
Good luck in your search... you certainly have a fascinating guitar there. Wish I'd gone to see it while it was just a few miles away from here.
