The Hamburg factory recovered strong after being bombed in the mid-1940s. It introduced a significant technological advancement in the 1950s - injection moulding. This allowed for faster, cheaper, less labour intensive, and more durable and reliable pen manufacturing. In fact, this technology changed manufacture efficiencies so much that the Danish and Spanish factories could no longer compete with the German one and so they seized operations eventually. The 34x, 25x, and 26x are the first few series produced using this technology.
To me, the 25x series has special significance in MB's history because of its unique nib design. The Montblanc wing nib was certified by the German Federal Patent No. 970 516.
It seems that designers were trying to address the issue of splaying nibs and the extra ink that would flood paper when the majority of its customers used too much pressure while writing. In order to prevent the nib from opening up under pressure, its design was changed from the typical curve to a flat front. The result - a wonderfully soft but not flexible nib. In fact, it was advertised as a pen with a soft and bouncy nib for expressive and flamboyant handwriting due to the novel shape and design of the nib. A Dutch catalogue says, "it will conquer the heart of the writer" while "alleviating fatigue and preventing cramping of the hand while writing".
For bibliography, see Resources page -->link