I recently received the attached photos showing a .223 case and a .40 S&W case. These were found in the desert at a place where people go to shoot in southern New Mexico.
The cases are nickeled brass with a purple stain on them. One close-up of the .223 case appears to show a cannelure just below the case mouth (possibly indicating a blank or reloaded blank case) though the cannelure is not visible on the other photo.
The question that the sender has is why the purple stain? My initial reaction is that someone has simply marked the cartridges in this way to identify handloads, but I have to ask if anyone has further information or thoughts?