When I checked my stockbook, I found I had five copies of the type sold by Viennafil: see the image above.
On closer inspection, I think all my five and the Viennafil copy may be from the same sheet. The basic shade of the 35 kopeck stamp is the same and - more to the point - the perforation is slightly off centre: the design is close to the perforations at top and left hand side. It's quite possible that only one sheet with this particular combination was produced: the large Z in violet is not common as a basic stamp.
The stamp is a nice example of a combined surcharge because the fact that the large Z is in violet and the 10 rouble surcharge in black allows you to see what has happened more clearly than when both overprints are black (I don't think they are ever both violet).
Anyway, Christmas is coming: if any collector wants one of the stamps above, then my price is 180 €uro with no extra charges for postage. I advise against the fourth stamp from the left which has one short perforation. The third stamp from left is with a tiny hinge remainder; the other stamps are never hinged. Probably, they all came to me when I bought the Tchilingirian - Ceresa holding of the Combined Surcharges.