Recently, there as been a lot of calls where older people got called by a fake police detective. The display reads "110" (which is the emergency number for the police in germany). So, if there are countermeasures, they are not effective.
Well, normally they use the call to get to know if the older people have something of value in their house. They usually tell stories that there has been a heap of crimes lately in the area, and that they'd like to help the people to secure valuable stuff.
If they have, they'll show up after some time, and collect it, to store it safe in the "police department" (which they don't, of cours). Or they'll show up as two, and one will pretend to do some questioning, while the second walks around the house and searches the rooms to find something of value.
That's at least how's written in the newspapers. So yes, it's a scam that is far more targeted, and not that easy to do - because you have to be physically in the area. Or you need straw men.
You can watch Kitboga on YouTube. He calls these centers and walks through the whole scam. Basically they use fear of an arrest to get the target to buy gift cards. It sounds dumb but it works on vulnerable members of society.
Source:
German Press release PD Westerstede early this year: https://www.presseportal.de/blaulicht/pm/68440/4174253
Follow-Up a few months later, warning that it's still an issue: https://www.presseportal.de/blaulicht/pm/68440/4358872