That would be the Magnum I.I used to use the Magnum II's back in the '70's and they were a pretty good head.The blades were stainless,silver soldered to a carbon steel ferrule.
That steel is hard too,though I never had trouble sharpening them.I have snapped a blade,getting too heavy handed,trying to pull one out of a tree but never had any problems on game.
I'm sure I still have a handful of those around here somewhere but they are the narrower version.I am thinking they were 125 grs but not sure if I should trust my memory on that one.does anybody know?
Anyway,a really good head.The fixed bleeder gives you fewer options in sharpening but it is still a great head and tough.