Dear Fernando,
Thanks for your post & your new photos and Thank you for re-quoted the post #25 sent by Estcrh
https://sirimunasiha.wordpress.com/a...la-matchlocks/
About the monogram appearing on the breech plate,the hypothesis regarding the letter AT seems very relevant, on the photos of the coins you posted we see a real similarity of font type and also An identical combination of the letter but reversed finally concerning the floral design I also recognize at least an influence.
best
Jean-Luc