11mm Austrian Gassar?

I have another box of treasure to sort and this one sort of stuck out. No headstamp at all so I went to measuring and the closest I could come was something known as the 11mm Austrian Gassar or 11.75mm Montenegrin.
The case is 1.39, overall length 1.75 and bullet diameter is .445. As you can see below, its a straight wall case.

Left is a .44 Rem Mag, Center a .45 Long Colt for comparison. Subject rd is on Right.

I’m looking for confirmation of my analysis and any comments on why there are no markings on the head.

Yes,you have a 11 mm Gasser ( not Gassar )Montenegrin round.My sample is almost identical to yours,same bullet without hds . Mine has a rounded rim and copper primer and was made by leon Beaux of Italy ( commercial round)

Thank you very much Pivi!