Sporting rifle cartridges by Gysemans

I’m looking for information on a series of sporting rifle cartridges designed in 1978 by Alfons Gysemans of Belgium. They were designated as “Jacht-en sportpatronen 55H” and share a common case 55 mm long necked to 6, 6.5, 7, 7.5 and 8 mm. Any help will be appreciated.