ID / BACKGROUND ON NECKED DOWN 7.92x57

Has anybody some more information on this 6x58 (case neck inside diameter is 6mm) which is a necked down 7.92x57 from 1897. I know there were trials with several different calibers which resulted from necked down 7.92 cases. This specimen was found on an area associated with the company BERGMANN.
The 3x120

looks like a 6 x 58 Forster

In Olson’s book on Mausers he states that one of the experimental 6mm ctgs was later made as the 6x58 forster.

Anybody else?

Can you post complete measurements? Please, dont’ forget to include body lenght, neck lenght and shoulder diameter. Thanks.

Why are the pictures gone so quick?

Fede, I do not have the case anymore so I can not tell the dimensions.