ORPO , Is the Police / Motorcycle card part of a set? if so just motorcycles?, how many?
Yes, the motorcycle pic is part of a set of police uniform postcards by Knotel. These are postcard size renditions of his large folio of around 13 color plates that he produced.
There are a couple of other series of police postcards represented in the array. There was a wartime series of black & white Waffen-SS cards that also had active unit police subjects and a series of Police Day color cards. The Police Day cards and First Day of Issue covers also had various cancellations that are actively collected in Germany by stamp collectors. Of course ther are also Police perfins and stamps that are found either separately or on cards or covers. Quite an array of postal stuff to collect.
Of course, I started out collecting world stamps as a kid so I come by this interest naturally.