German WW1 77 mm proof shot shell?

[Der_Feldgraue]

Hi,

I just got this german WW1 77 mm shell. I was told it is a proof shot shell without fuze/charge for testing new guns. I suppose it was filled with sand or something like that. Does anyone know this type?

 

[Der_Feldgraue]

Nobody? :cry:

 

[Der_Feldgraue]

Nobody knows this type of shell? Is it that rare? :xd: