Here you go. I will see if I can get better images. In the meantime, your aluminum forging is riveted to the upper tank ( Alcohol ) of the V2 and is where a type of stabilization rods are connected to hold the tank in place. The rods are connected through the bolt hole in the forging and travel down to the connection rings of the warhead. There are ball joints at this connection so the tank can be balanced, etc. We know your part is from the upper tank as the lower tank forging has 9 staggered rivets across the edge, while yours has 7. My image is of the tank already mounted in the rocket body. You can visualize the forging without the bolt and rods connected. The exterior tank image in online from NASM. Your panel is at the right end of the tank image, the larger riveted panels. The smaller panel actually holds the tank into the side of the body. No doubt when the rocket exploded these tanks blew apart as your part seems to show.
Tony