How many charges does Greagan's Harp, Horn of Kazgorath and the Staff of Striking have?

Unlike with wands etc. it's not possible to see how many charges Greagan's Harp, the Horn of Kazgorath and the Staff of Striking start with, does anyone know? Can either of these be sold and re-bought with more charges, if so, how many charges do they have on re-purchase?

Also does the horn always do the same damage to the character when used (10HP?)? Thanks

I have an evil Jester in mind for both the Harp and the Horn, which seems appropriate...