Yep, probably steel jacketed. Tough bullets, intended for really big game that needed a lot of penetrating. I shot a few boxes of their .44 Magnum in the mid 1970's, and yes it was stout stuff.
They do have a steel jacket. If I remember correctly they are coated with a nickle alloy, quite commom with European rifle ammo as well.
In the 1960's I used the factory Norma ammo and reloaded their bullets as well in my Ruger 44 mag Carbine. I killed quite a few deer with those bullets. Never recovered one.
Saw an ad in the Nov-Dec 1971 Handloader #34 for Norma Tri-Clad bullets. They had a welded three layer jacket of gilding metal/soft Swedish steel/gilding metal to give controlled expansion on tough game. Stumbled on a few boxes in a friends estate sale. Haven't tried them yet. they look like nickel or silver.