Thank you so much, 'Nando,
Actually I like your copmrehensive approach far better than my humble try. I just tried to gather it together from my memory.
Yours sounds much more convincing.
Anyway, the first real muskets according to my definition seem to have come from Spain, their characteristic broad triangular butts soon becoming typical of the whole category, especially soon in the muskets of Hispano-Netherlandish type in the 1560's-80's made immortal by de Gheyn's engravings in 1608.
Best wishes,
Michl