Poldi is famous because of the furnace that was used.
http://www.poldi.cz/steelworks

Beretta was an early user of them for barrels. Poldi produced various formulations over the years. There is a good discussion about that here:
http://www.migratoria.it/forum/armi-e-caricamenti/37341-tipi-di-acciaio-canne-beretta.html

Pete