Hi Stenoyab.
Just when I thought I've seen everything. LOL.
That is the most unusual - and interesting - feature on a Torador matchlock that I've ever seen.
As Richard says.....it does look like an invention/addition to the gun at the time of manufacture. (?).
But it is certainly cool !!! Never seen/heard of one before. Richard's guess as the reason for the fake pan is as good as I can guess for the moment.
This highly unusual feature alone would be justification for restoration IMHO.
Speaking of restoration: If possible, could you provide some photos of the complete gun as well as photos of the areas of missing parts? I might have some original parts you could use (?) such as this original trigger assembly
PM me if you prefer.
Thanks for Posting this really unique feature on a common gun.
Rick.