This is a knife bayonet used from the period 1891 into WWII and was designed to fit the Italian Model 1891 Carcano Infantry Rifle. There are several bayonet sub-models: Model 1891; Model 91/97; and Model 87/91/15.
Within the first model are at least 5 or 6 known variations, but all with the same basic style and a side-mounted realease in the pommel;
the second model has a unique locking arrangement with the release on the butt of the pommel; the third model usues a Vetterli-Vitali cross-guard
All models have wood grips, steel pommel, crossguard, and blade.
There are at least 3, perhaps 4 known scabbard variations and I have owned 3 of these: sheet-steel-mounted black leather; brass-mounted black leather;
and sheet-rolled-steel (entire scabbard) with flutes (2 grooves/3 ribs) down the side. Two of the most common scabbards are shown.