Grandson's Artillery Find at the Somme WW1 battlefield

My Grandson has just returned from a school trip to the Somme Battlefields. I had given him a map of Usna Hill near La Boiselle where his g, g, great Uncle was KIA. Running down the hill my Grandson stumbled and turned over the item I show below.

It is 7cms high, 6 cms diameter with a weight of 920 grams - seems to be made of brass and has degradations around the cone

Does anybody know what it is?


AND more importantly how should we get it cleaned up?

 

Another view

 

That's an Artillery detonator/ fuze appears to be a time delay type.
U.S. Artillery Fuzes, 1960's to Modern - Inert-Ord.Net

 

Thanks - that was my first thought. Do you think the mechanism might still be intact - here is the base.





Any ideas on how to clean it up?

 

Looks like the part that actually goes "BANG!!!!" is gone; but, have someone look at it that knows what it is to ensure it is safe. My guess is that you have the mechanism and not the accelerator portion, and judging by this picture it looks to be German:
here is a pretty comprehensive site:
Passion & Compassion 1914-1918 : WW1 militaria and technical documentation - artillery fuzes

 

Thanks everyone for your help.