Well, since I shoot at a private club range and there's never anyone using the same range as me, and I pick up every piece of reloadable brass I see whether it's mine or someone left it, it's not an issue to me. I won't leave any of my modified cases unless one hides under a rock or something.
And when I sort my picked-up brass, when I get to the 9mm size I stand them all up on a tabletop in one big mass, like a crowd of pilgrims waiting to see the Pope, and then it's very easy to see any .380's or 9mm Maks that are in the herd. I just use a pair of tweezers to pluck out the non-Lugers and move on. I actually do that with all auto pistol cases, makes it very easy to find the .45acp's, .40 S&W's, and any wierdos like .45GAP or 10mm.
I have a set of those sorting tray things, but when the cases just nest together those things are useless.
Besides, my PA-63 has a broken ejector at the moment, and finding one had has been a fruitless search. Seems they're made from unobtainium.