[Shakethetrees]

You need a screwdriver that fits the brass pommel nut. Grind a "U"shaped groove in the center deep enough to fully engage the slots on either side of the tang and unscrew. When you grind this, make sure the screwdriver blade is kept cool or you'll lose the temper!

I would take note of the fiber, brass, horn, (or whatever), spacers and use some CA cement (superglue) to fix them into alignment. Do this away from the antler grip. Make sure alignment is perfect and let the glue wick in between the layers. Once it has set this can be handled like a single unit and glued to the antler.

After the blade has been cleaned and polished to whatever degree you prefer, stack everything back as before and screw the brass nut down snugly enough to where the pommel won't turn.

This type of restoration does not involve any real tricks or technique, just forethought and a bit of elbow grease. Work slower rather than faster and constantly check your progress.

Oh, and use hot wax on the whole piece...

Then,

You're done!