[Jim McDougall]

The 'main gauche' thing is IMO a bit overplayed usually, these pretty much fell out if use, at least in the fencing aspect by the end of the 17th c. but daggers, presumably of this basic form did remain worn as secondary weapon. While fencing was typically not necessarily a duel to death, in many situations involving sword to sword combat such as brawls or melee in civilian setting (i.e. Italy as in Shakespearean dramas) the dagger became key when close quarters tussle rendered further use of sword/rapier impossible.

Though this example seems to have the presumed look of a misercorde, that particular weapon had not been in use for some time, these were of course allegedly for 'coup de grace' to mortally wounded knight. While this rather dramatic notion was popularized in the annals of chivalry, these were more for the same close quarters combat as they were intended to penetrate any open area in armor whether gaps or damage.

That the classic design might well have been carried into the theme of this interesting example seems likely, and the intriguing six point star in cartouche seems to have a symbolic character as in architectural motif, more research would be most interesting. The blade seems aligned with daggers of late 16th to 17th c. but I would defer more on that to experts.

Egerton Castle, "Schools and Masters of Fence" (1885) examples 8,10,14 , plate IV, shows three examples of this basic form as cross hilted daggers of Baron de Cosson, coll. 16th c. Italian seems likely, but of course hard to say as Italian influences strongly diffused into other arms centers.