A note of caution... Once, while out socially, we were standing in line to get into some joint. A fellow ahead of us was talking with his buddy, facing us. He pulled his coat aside, revealing a black leather "holster" affair, and reached for this item in a manner entirely similar to someone about to draw a pistol.
I was armed at the time, and was readying a "clearing" motion myself when I saw that this "holster" was some species of wallet....
Perhaps not the ideal thing to have in some circumstances, practical though it might be.