This spirally rolled up spring used in some Japanese matchlocks is not recorded from any surviving 16th c. European, esp. German sample. On the other hand, it just seems a more refined evolution of the rolled up cord for spanning a wheellock, in a sketch by Leonardo da Vinci, ca. 1500-10 (first attachment).
Spiral springs of different device are known from one or two ca. 1550 wheellock arquebuses in the Real Armerķa. Madrid, though; they seem to be based on another drawing by da Vinci (second and third attachment).
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