Is there any evidence it had a hinge pin and catch?
Looking for LDO marked EK2s and items relating to U-406.....
You can see solder marks where some sort of catch or pin holder was at one time. Two of these came in a collection and neither of them have the attachment pins and both look the same. Here are pictures of the other badge. You can see where a pin was attached at the top of the infantry assault badge. There is a light solder mark on the bottom as well.