They aren't stamped. The blades are blocked out but the hollow handles are then welded to the blades after being filled with the right amount of sand to balance them perfectly. It isn't possible to forge or stamp a hollow handle. The blade steel is RC 57-58 so they are harder than European or American kitchen knives which usually run around RC 54-55.
Incidentally, there is no advantage to a forged blade in a kitchen knife. Knives are forged in Europe (Wusthof, Henckels etc.) in order to form a bolster. If they make a knife without a bolster, they just block it out. These days they don't even drop forge them. They use a pressure forging process. There is no other reason to forge a kitchen blade except to form a bolster. The Japanese forge weld a separate bolster to the blocked blade instead of forging the whole thing. It seems to work pretty well. An example of this construction is the Shun Classic series.
Most kitchen knife experts place the Global line as somewhere more desirable than European or American knives and somewhere less desirable than the higher end products from Masamoto, Suisin, Kikuichi etc. All in all, they are very good kitchen knives and they really do balance perfectly from the longest slicers to the parers. Other manufacturers worry about balancing just the chef knives and letting the others fall where they may. It is a unique feature of Global G and GS series knives.
