Pete,
we have this info in CartWinPro
"Case made by Starline, Missouri. / Info fom Starline 2020: "I believe that we made that case for Atlanta Arms several years ago. It was just a regular 9mm case, with a custom headstamp, that they loaded to higher pressures than standard 9mm." (Thanks to A.Martin@APD!)"
Hope this helps
Greetings
Axel