Austrian 105mm low recoil tank gun steel cases

I am searching solid info on Austrain made (Hirtenberger) 105mm low recoil tank gun (M57) cases made of steel.
To be exact I am interested in the headstamps (images).
I did only a brief search and was not really able to establish the origin of the case design which I assumed to be French GIAT but their 105mm has a long and shallow shoulder while the design in question is cylindrical. I checked on Belgian MECAR but the only one I have found now was a straight walled 90mm.
I am sure I have some docs somwhere ID-ing the origin of this case but can not locate it.
But as said for now I am after the headstamps on the HP loaded rounds.

Here an image from an undisclosed Austrian military document.

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Update for myself and others if anybody cares.
The system appears to be a French design (Mle57) which was used in the AMX13 (in Austria designated “Kürassier”, English: cuirassier).

The case is a 105x528R (as per Hawkinson’s caliber list).

So for now I am still looking for headstamp images of such steel cases.
Anybody?

Here a flyer from Hirtenberger:

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