Brief story with pics on 2 Race Face ahead stems with interesting adjusting/clamping mechanism. Here Ti stems featured, but there also existed steel and Aermet ones! I heard they are Dekerf made.
I weighted the 2 Ti's: One (I think the older) is lighter than the other (180 vs 225gr). The later has rotating headset adjusting part that is beefier and grippier (for your hands). The light one has a flatter round piece. The clamp (located inside) differs too. On the light one it is a wedge like we know from regular stems. On the other there are two bits that expand a cylindric piece (with slot). The later can be converted to 1" too, if you have the right bits. Maybe that was one reason to come up with the redesigned clamp: standardisation.
Right the somewhat lighter stem (approx 185gr). I think it is earlier, but I am not sure on this. The other stem weighs around 30-35gr more.
The more recent(?) stem with more sophisticated clamp:
1-1/8'' (left) and 1'' assembly caught in one pic