Oh, how nice to see some European arms on this forum from time to time
. It is Mediterranian knife indeed, it's seems to be very popular in Italy. Try to explore some Italian arms & armour auctions and I think you'll find plenty of similiar weapons (in the past I saw on Czerny's auctions few of them).
Yannis: are you sure this is end of the 18th century? Can I shyly suggest mid 19th century? It's not expert thought, just a feeling when you look at the sheath, at brass fitings, etc.
By the way, aren't similiar knives mostly seen without scabbards nowadays? Anyway very interesting object, and thank you for sharing with us with this piece of European history
PS. Congratulation long history of your family, I love genealogy, but somehow I'm happy my familiy roots riching "only" to 14th century