Jørgen from denmark send me pics of his new acquired 16 ga Manton double gun and there is a question about it.

"The "gun" came home and while made 1815 it does not actually seem like someone has open in it since it was born. Ok there's some rust that's going to go away. The stock is somewhat dark, but appears to be really good when it's cleaned.
It's a cal. 16, easy with a very good balance, just like my Purdey and Alex Martin. Just as Thomas says, a gun in wood and steel, craftsmanship in the best class, without CNC machines, without turning and file tracks, all polished, very tight in all sidelock, and do not bear the feeling of being used much. Now, when you look at the side lock, yes, all screws are ok. The hammer are as normal at this time "dolphins".
The barrel are "rose-damask" best quality, proof and stamped in London. And also absolutely amazing engraving. It was possible to loosen and get all the screws out and only one wooden screw under the trigger clamp, which was stuck firmly, broke.
Still, I do not understand that I was lucky to get it at the low price !!!!!!!!!!!!!!
Manton is considered to be the father of the shotgun , as we know today, and I understand now.
I have got one in my hands for the first time and only before seen pictures of them."
The Manton, SN 6778, is from 1815 the time when we began to rebuild flintlock guns to the new percussion lock."

pic of a Flintlock SN 2636 made in 1797

now the problem:

"I've seen photos of some and everyone has the “white spot” just below the hammer. It looks like an aluminum plug, but I think it is not.
Think there's a screw below, whats the "white spot"????"

other guns from this video https://www.youtube.com/watch?v=pk46oQ0owls