This pubic apron / cache-sexe, also known as "nzenze", is from the Kamba tribe, in Kenya (also called Akamba, or Ukambani). It has been bought by me and my wife (along with the other one I have for sale here on ebay) during a trip in Kenya back in 1971, and the person who sold it already mentioned it was old/ancient. 

A couple of years ago, I spoke with an African Antiques expert, who told me it was from the 1920s/ early 20th century, and confirmed the Kamba origin.  I saw a similar apron at the British Museum, and in other museums in the USA online and, actually, style, age and provenance correspond.

The metallic ornament in the bottom part is probably an antique watch chain. on which one cent coins used to be attached according to the tradition.

Dimensions: 28 x 14 cm

Weight: 200 g

 The public apron (nzenze) is worn by young girls and unmarried women during competition dances between rival villages.
The apron not only enhances the wearer’s appearance but it denotes a value - the value being determined by the amount of beads being worn. Through this it is the boyfriend who assesses how much the girl’s father is worth.
Upon marriage, the girl will give her apron to a maiden in exchange for a goat. Before selling it it is obligatory to remove a part of the apron such as the tying string or a one cent piece to avoid bad luck.  Each apron is hand-woven who threads the beads using boabab (Adansonia digitata) or sisal fibre.