Not a Bad Idea / or not...
"Originally designed for law enforcement officers, the designers of the DSM Safety Banner thought, that the American citizens also deserved a way to immediately identify themselves if they became involved in a critical situation where uniformed officers response was imminent. No one had ever considered a safe way for legally armed citizens to identify themselves with 360 degree efficiency to responding law enforcement officers. " From DSM website, link above
Although I think it's a bit pricey, it would be perhaps an aid in not getting shot, but it is one more thing to carry around, (I have thought of a "drop down" panel that might say "Armed Citizen", but I don't always wear the same outer garment)