This is a knife bayonet, manufactured from the period of 1889 to about 1915, and was designed to fit the Belgian 1889 Mauser Rifle. This short knife bayonet is very similar to US-made Remington "Rolling Block" bayonets sold to Mexico as the Mexican Model 1899; it is also very similar to the Uruguayan Model 1895 and the Venezualan Model 1900.
A longer version of the Belgian Model 1889 also exists; this bayonet was produced in large part by the U.S. firm of Hopkins & Allen. It is very similar to the French Model 1914 made by Remington with the main difference being the distance of the muzzle-ring from the blade (the 1914 is closer).

Hilt has "bird's head" pommel, push-button/internal-spring latching mechanism, steel crossguard with lower hooked "blade-breaker" quillon with ball finial.
Single-edged, knife blade is fullered on both sides.

These are not rare, but they are scarce in good condition.
The scabbards are sheet-rolled steel with ball finial on tip.