Origins of African Ceremonial long dagger/short sword with aluminium handle?

[katana]

Newest addition to my collection. This dagger/short sword is relatively sharp, with a dot pattern (serpentine ?) running down the centre of the blade (both sides). Blade 37 cms long, 4cms at widest point, good patination and tempered steel.
The handle (24cms) is aluminium, heavily encrusted with oxidation, it appears that the handle was cast with the blade inserted. The handle was then hand worked, and incised with a 'criss-cross' pattern on the raised banding.
I do not think the scabbard is original to the blade, it fits very well but there is a flap (which is a later addition), which has two leather 'toggle' type straps which secure the handle perfectly. The scabbard has a shoulder strap.

The 'crown' (?) pommel is very interesting, and overall I extremely happy with it . I believe that this was originally made mid 20c, perhaps a little earlier.

ADDITION. Whilst 'playing' with this, I found it was very comfortable to use two hands on the handle, the raised 'points' just above the 'crown' fit between the fingers, the 'crown' fits neatly in the clenched palm (left hand) and gives a lot of control. A two handed short sword???

Can any one help identify this piece or its origins? Also I am reluctant to clean the handle, should I or should I not???