Ebony was never used as stock wood as far I'm aware but some late Mk 3s did have very dark stocks, which looked to have been varnished. I think walnut was used and then stained and varnished.
John
I am sure that Ebony was never used, I had a Mk3 bought from York guns in the 1980's and the stock was almost black.
I would concur with John that it was likely stained before varnishing.