Unknown rimfire cartridges

Hello,
I have posted about these two rimfire shells a few times in the past but have had no luck.
I believe they are both 27 caliber, one of them has a SI headstamp and the other left blank.
One stands 8mm y’all whole the other stands just under 10mm tall.

Any information is appreciated.

SI or SL ?

I assumed SI but the bottom of the “I” is where the casing was struck, so it may be SL

if SL it is french and means Souzy and de Lacam

Could you make a bigger and closer view of the hstp ?

jp

Hello, the lettering is very worn and hard to read. Please excuse the bad pictures as one if through a microscope to show detailing of the letters.

Another weird factor I have seen on these shells is the strike marks are abnormally large compares to any other rimfire shells I have seen.

Thanks, Hamish

I should also ad these cartridges were found at an old gun range in south Australia, right on the coast of Port Macdonnell. However I have found cartridges dated many years from 1916 to 1962