These were one of the lampwork types made as jewellery beads rather than for trade, so not generally found much in Africa.
You found them in Europe, didnt you?
I have a number of them in different colourways, both spherical and pointy-ended oval. The colours (of mine) are not so typical Venetian, they might well be Czech/Bohemian.
A characteristic is that among the one or two of mine that are broken you can see the pattern is not merely on the surface but the body of the bead has half in each colour, swirled and spiralled around the equator (like stirring treacle on a hot custard pudding), and including a band of avventurina glass.
My reason for suspecting non-venetian manufacture is that some I have are half translucent maroon, half "greasy yellow", others are cream combined with translucent purple. These glass colours are much more familiar in Bohemian glass jewellery.
As to their date, I have had them, same colours in graduated sizes on long over-the-head strings in the 1930's style.
Although the clasp isnt shown, its likely to be another clue suggesting
Bohemian, and the cord which looks to me like the flossy rayon-type "artificial silk" embroidery cord that was often used at that time.
Stefany