I just assumed that there was a .50 cal cartridge beside the plaque but not in the pic...
I thought that at first, then I wasn't sure, I think when I was there something else made it seem like it wasn't actually the same rifle. There is a .50 cal cartridge in the picture if you look beside the bolt. It would have helped if they lined the plaque up with the cartridge or something to make it obvious that they were refering to it.
All that to say, I dunno.