The parts in the picture seem to be plated with something. Removing the plating could be informative (sandblast, etch, or even manual sandpapering could work).
The magnetic part could be 1018 (a carbon steel with relatively low carbon content). It could also be lots of other things. The non magnetic part is not carbon steel, might be stainless, or lots of other things.
I agree with the opinions above that the part appears brazed.
If I was tasked with manufacturing these I would at least look into furnace brazing. It's reasonably low tech, at least from the operators point of view, the whole part is heated and thus will probably not warp badly, and the equipment is probably cheaper than cnc.
Bill