Actually, I have quite a few of the silver colored Norma bullets in 5 diameters.
[6.5mm/139; 270/130; 7mm/150; 308/180; 8mm/198]
The jackets are mild steel, and magnetic.
However, the guy at Norma who said they only made those and the newer copper
colored, gilding metal is off base. [maybe a newer employee?]
I just opened an older box of Norma bullets [it was sealed] in 30 Cal, 150 grain RN with a small boattail.
The jacket material is neither gilding metal not MS. It is brass-colored, just like the ones in the OP's post.
I opened another sealed box of Norma Bullets, 180 grain Semi-spitzer boattails. No cannelure at all, but
guess what? Same brass/bronze color. I have also seen a 6.5mm/139 grain Norma bullet that looked the same.
Neither of the last two bullets is magnetic.
FWIW, the old, MS jacketed dual-core Norma bullet was a very good game bullet, even at 308 Norma Mag speeds.
Regards, Dave.