Guy: I have a later version which is definitely Goncalo Alves, and one I am not sure of. (first pic side-by-side with the above grips). From the more open grain on yours, I would have guessed Rosewood, but I don't have many samples.
The pics below are on a fabric which is close to neutral grey.
First pic is the grips I asked about above, and a Goncalo Alves set from late 50's~early 60's).
Second pic is same grips and darker walnut N magnas from ~1960, s/n 203xxx. None of the grips are as nice and shiny as the ones in your pic. More satin than glossy, but I believe original finish.
3rd pic is all three sets, walnut magnas in the middle.