Found some info for you. It appears that the mud guards you see in the picture are a very early type of May 1942. They were made of what we would call diamond deck. There are three textures they were made from. Diamond vertical, diamond horizontal and a square like material. It was also after this that the hole was made on the glasis near the fender. This was for a jib boom that was used to remove the sproket. Some say it was used for a pole to hang cammo from, but I found otherwise.

As for the resess, I have no idea. The taper you drew might...might be the angle the picture was taken from.

Hope this helps


Don