Strand length 36 ins / 90 cm - the beads, which graduate from 10 x 14 to 26 x 38 mm
have a lovely smooth and waxy feeling with varying degrees of opaqueness .. weight 363 grams
I reckon that those beads were made of rhino horn -- a substance that I got to know quite well during my stint as an assistant keeper in the Department of Ethnography in the British Museum, special responsibility: N. S. and E. Africa. Especially in E. and S. Africa, rhino-horn clubs were part of the equipment of a well-kitted out warrior. I have checked and the longer (front) horn of the black Rhino can reach 120 cm in length, that of the white Rhino averages 0.6 m long and often reaches 1.5 m long.
My guess is that this string of large horn beads was the result of making the best of such a club after the knobby head of it got damaged thanks perhaps to insect or rodent attack. The handle would have been long and slender, whippy even, and the head not all that large, maybe the size of a small orange. Simply cut the handle into sections, bore centrally, and shape the beads as if they were sections of a broom handle. Rhino horn is made of compressed hair -- once seen the 'grain' is unmistakable, and the concentric rings effect visible at the perforation aspect would fit in well. One club would make such a bead string easily, whereas you would have to kill a lot of cattle to get so many solid horn tips !