Originally Posted by Philip
Just discovered this illustration in Alarico Gattia's Fucili e Pistole (Milan, Rizzoli Editore, 1968, p 40. Three versions of the lock commonly known to collectors as "miquelet" are shown. On the left is the traditional Spanish version in pretty much its pristine 17th cent. stylistic format, which was widely copied in Italy (primarily the southern half, but made for export in Brescia as well. Major points for comparison, germane to this thread, are the wasp-waisted lock plate, mainspring leaves of markedly unequal length, the reversed frizzen-spring largely concealed behind the priming-pan shield, and the obtuse angle of the cock jaws to the columnar stem.
On the far right is the typical Sardegnan version of the above -- mechanically identical but stylistically distinct in terms of the four design elements identified above.
In the center is the central Italian version of the miquelet, very popular in the regions around Rome and Naples, commonly known as the Roman lock (acciarino alla romana). The most notable points of departure from both of the above is that the mainspring exerts force in the opposite direction (downward, and on the toe rather than the heel of the foot of the cock), and a sear system (the levers and springs that link the action of the trigger to the release of the cock during firing) that is markedly different, being derived from that of the typical wheellock.