I'm going to go out on a limb and suggest that the caption is in error, and that the photo shows the wreck of 503 (C4) "Chablis", which broke down near Pozieres on Sept. 15, 1916. Although it is blurry, I think that "C4" can be made out on the front horn when the image is enlarged. The first section of C Company, which included C4, did not carry the grenade roofs seen on tanks from the other sections of the company. The photo below shows the same wreck in May 1918.