That was a broken turnscrew blade not screw head.
I'm sure JJ could replace that, or you could have it done locally.
It was the very first thing that caught my eye as I opened the case too, I left it in it's place for a while until I'd gotten my eyes on the rest of the contents.

Those bores really are pretty.
Did you catch the light color of metal fouling on the lands?
Had George or JJ shot this rifle prior to shipping it out here to the west coast?

--Tinker