Projectile Head ????

I've just come across this article which is being sold as a 'paperweight', although it is obviously intended for some other use.
Despite my almost non-existent experience of militaria items, I get the impression that it is actually a former shell head that screws into another head or casing. There also appears to a type of scale at the base of the item - perhaps an adjustment for distance, angle, or even a timer ????
The item is c. 6cm high.

Although I normally don't collect militaria, I'd neverthess less be interested to find out exactly what it is.

Any help is much appreciated !!!!!

 

Fuze