These are a couple of samples showing two types of grass cutter bar made by the German company Lanz in the early 1950s. Lanz is better known for their hot-bulb oil burning tractors.
The first (above) is unusual to me, the knives are on a different pitch to the guards. I don't understand how that would work, the stroke must be 1.5 times the spacing distance of the guards.
The second (below) is the more common today, the knives center on the guard at each end of the stroke.