I don't have a overall pic of the gun, but I have this clip of it - at 7:25
This video was shot by a couple of journalists, and the guy explaining is the owner of the gun Søren - a danish gun collector and spearo.
Sørens passion for harpuner - YouTube
The handle is a sort of sliding tenon, a center part of the grip with two grip scales glued on.
This gives a huge gluing surface. It will never come off.
Ah, now I can see it in the photos and it explains what I see.