I think David Herbert is spot on with it's use as a closer look at the many photos I have, I can now pick something in the photo attached. The shape of the pyramid had me puzzled but the photo puts it in total perspective. In the first photo you can see a tray on the left that would hold a Vickers ammo box and it is shown on an angle that would fit perfectly into the recess and that part is on the curved section of the turret on the same side as the Vickers. In the second photo on the right, you can just see the beginning of the open recess I will get confirmation on this but I am confident that is the answer.
Half the fun is solving problems and questions and learning.
