Hi Spiridonov,
Brilliant questions.
Let me try and answer them as precisely as I can. I attach the images marked by you.
1. The design on the buttstocks of these early (h)arquebuses is not a lock plate or a stylized mechanism but a carved double volute ornament.
2. The arquebuses illustrated in Diebold Schilling's
Lucerne Chronicle of 1513 are ignited clearly by means of a snap tinder lock (tinder is a kind of fungus growing on trees and was lighted by the smoldering matchcord) but no details are shown.
3. The dating of this arquebus is based on the shape of the early Landsknecht (mercenary) buttstock and the barrel with its integral back sight at the extreme rear and no pronouned muzzle section which somtimes occurs between ca. 1470-1500.
4. The snap tinder lock mechanism of the gun no. 3, of which only the main spring is retained, was nailed or clamped to the stock and certainly looked a lot like the ones on the Pilsen arquebuses - with the exception that the small serpentine plate was not present yet.
Regards,
Michael