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IIRC there is the fully milled "H" style (first style) then they started changing how they made them to save time in manufacturing. Next is milled with no "H" cut, then stamped, then stamped and welded.
Some of the late stamped bands will also have a drilled screw hole (front band secured with a screw in the last steps of production) vs a pressure band.
I think these were only seen on 1945 rifles, but I would have to check my references (Kriegsmodell Vol III) which is a few hours away from my location.
Some variations pictured here: http://www.latewar.com/html/kriegsmodel.htm (This website was run by the authors of Kriegsmodell).