The use of buckshot (the Germans call it "Posten", the British "slugs") on any hoofed game, be it deer or boar, is outlawed in Germany for 100 years by now.
The history of shotgun slugs that could be shot through choke bores goes back even farther. AFAIK the earliest was v. Witzleben's "Bolzengeschoss", essentially a stick of very soft wood with a blob of lead cast onto the front end, of the 1880s. In 1898 Wilhelm Brenneke patented his first slug, a ribbed lead cylinder stabilized in flight by the felt wad fastened to it. This design he developed over the years into the Brenneke slug we know today. There was competition from other designs pre-WW1, f.i. the Stendebach, Oberhammer, Kettner, but these all fell by the wayside over the years. The French Bougnet was of the same design as the Foster, but predated it. The Brenneke outlived all the competition. In Germany "Brenneke" is used as sort of a household word for any kind of shotgun slug, be it of old Wilhelm's design or not.
In Germany slugs were, with one exception, never meant as primary hunting armament. Instead, hunters carried a couple of slug loads in a pocket on hunts for hare and feathered game just in case if a boar would show up. Now, with the increase of wild boar numbers, most slugs are used on these animals. A drilling, loaded with a decent rifle cartridge, a shot load for hare or fox in the right barrel and a Brenneke slug in the left barrel makes a decent "Ersatz" double rifle for short range use on wild boar.
The exception was the GDR: As the commies mistrusted all their citizens, all hunters had to be rated "politically reliable". Even so, ordinary hunters were not trusted to own a rifled barrel. Maybe one of them might snipe at Erich Honneker or Erich Mielke, the head of the Stasi, the infamous secret service. So the ordinary GDR hunter, if trusted with owning a gun at all, was limited to a shotgun. So he had to use slugs with their limited range for all his big-game hunting. Many of these poor guys had scopes mounted on their double barreled shotguns (no repeaters in the homeland of workers and farmers!) to improve low-light usabilty.
