Hey Mart,
I know you can't see it in the photo, but yes, it is a bullet mark, you can still see the lead splatter mark on the steel, I'll try and get a better photo of it tomorrow when I'm at my buddies store. A small caliber firearm like a revolver a 32 or 38 would leave this type of mark on the plate, by the way it weighs in at 20 lbs, could be a shed piece or a privately made piece
Regards,
Kevin