I believe that is an add on Skipp.
Here's mine...you'll see where the previous owner (?) installed a mudflap on mine...where your box is attached at the front.
Looks like someone added two holes in the motor plate of yours, so as to attach the back of the box. (I keep calling it a box...because it reminds me of one, it looks like a good place for a battery box for an electric start motor.)
@chatten63 ...Rick, was there a mudflap or anything attached there on a 'new' super bronc ? Thanks.