This copper alloy plaque bears the initials BBF in capital letters, and two dots separate the letters. With three corners of the plaque intact, we can be confident this is all that was originally written on it. There is no trace of the letters on the back of the object, so it seems likely the letters were punched onto a flat bronze plate. The force of the strike seems to have been slightly uneven, so that the edges of the letters were the first to corrode and break.
As always, if you know what this object was, don't hesitate to get in touch.