I'm not sure on the maker but most makers are in or near Bresica. 76mm(3"-approx.) is the depth of the chamber while the 18.4mm is the diatmeter of the tube just ahead of the chamber at a specificed distance from the standing breech. The single star notes the choke for Italian longarms and is full; not an exact number but a general designation. The KG 1.480 is the weight of the tubes in kilograms; while the 3 stars is modified. There should be a date code on the flats like XX or XXIV.
Kind Regards,
Raimey
rse
