here they are, 1926 ICI Eley Kynoch catalog

the lethal bullet looks similar, my guess the rings around were a little bit oversize to give a tight fit in the barrel than also allow to pass the choke bore. probably with the side effekt of lead in the barrel build up quickly.looks like the bullet was hollow with some cross struts inside to make it lighter than a common round ball so I think two half were pressed together.