Hi 'Nando,
As snapha(u)nce arms are not exactly my main subject, it was sadly only now that I found your thread.
I am quite sure that your ball-butted or pear-shaped butt pistol (puffer) is of English origin, ca. 1600 to early 17th c., in its main parts.
The shape and decoration of the barrel tang and the fore end bands denote that they are later working-time alterations the decorations of which show some Oriental or Southern Euroean influence.
English pistols of the Late Renaissance period are extremely rare to find in unaltered condition.
I attach a similar but unaltered English specimen of a 'puffer', the trigger and guard missing, in the Doges Palace, Venice, and an image of another in an unknown collection.
For stylistic comparison, the one at the bottom is also English but of the Cromwellian period, ca. 1645, also in the Palazzo Ducale..
For more on snapha(u)nces, please see
http://www.vikingsword.com/vb/showthread.php?t=14112
Best, my friend,
Michl