12 bore Banshee

I received e-mail from someone in southern England who is trying to sell a box of 100 Eley 12 bore “Banshee” cartridges specially loaded by W.C. Carswell Ltd, Gunmakers, 4A Chapel St. Liverpool. He assumes they are from the 1950s. He is trying to locate an auction house that would sell them for him. Any ideas??