Thanks Katmaxoz for posting. I do not know if this is it. I have never seen one.
I enlarged the blue circle stamp and there is written "Avanzo. St. Petersburg Gr. Morskaya no. 9". Does that sound like an Imperial stamp?
No, this is not the Imperial Court Censor stamp. It is from a dealer who later sold the photo. It will be a long sentence in Russian, referring to the Imperial Court itself. I know we have several in the archives and I don't have time right now to go through the boxes, but will keep my eye out for one.