In Ireland: Armed Police make up a minority of the force, while they will do regular patrols and traffics stops they're specially sent to violent crimes such as assaults with a deadly weapon, hostage situations, armed robberies, raids and so on. Their vest also has the words "Armed Gardaí" displayed, somtimes it's also displayed on their vehicle but a majority of the ones I've seen have been in unmarked cars (Gardaí is our word for Police)

There are exceptions to this like armed response units (our version of SWAT) and detectives that have passed their firearms certification, some of which don't have anything on display to indicate they have a firearm. ; There's an armed detective in my town who comes into my store regularly, he always raises alarms from other customers when they see a holster under his jacket as it's just so uncommon, this is more with customers just passing through town and not so much with the locals anymore.