The only ones I've ever remarked have been some 8mm Mauser (8x57)made into 8mm Mannlicher Schoenauer (8x56).
I did that for my own sanity should I ever get them mixed, they look so similar.
The Remington brass I use is headstamped 8mm MAUS. The stuff I convert, I change to 8mm MAN/S by a couple of simple engraving cuts
Anything else done in the way of conversions I just keep separate, lable the boxes like others have said and if you want to, mark the heads with a laundry marker. It'll last a long time.
Some reloaders use a system of very light, small center punch marks into the head (small!) denoting for them, it's actual caliber rather than the headstamp. Doesn't help the brass scrounger, but it can help you keep things in order.
As long as you can keep things straight,,don't loose much sleep over a 'what if'. You're not selling or giving this stuff away to un-knowing persons after all.
It's your hobby,,have fun.