Those rivets are mine but they did replace exactly the same so that is still unusual. But solid rivets would not have been used on a perforated grill either as they need solid casing holes in both materials being bound so as deformation only occurs at the back of the rivetIt's aluminium pop rivets drilled through a badge. No way any badge left a factory with drill holes and pop rivets. Would have been mounted from the back of the badge and hammer rivets were still on use more so at that time.