very interesting beleg2, I try to make it something bigger

it looks like a cats head bullet with a brenneke wad. if this is around 1938 and was new in this time it may be the reason its unknown today, the outbreak of WW 2 in 1939 stopped it. there was an italian made over/under 12 bore 10 years ago with a rifled and a choked barrel. when I see it right they make the "Ideal" gun in 20, 16 and 12 bore. the MF slug was available in 14mm (32 ga), 24, 20, 16, 12 and 10ga but not in 28 ga.