Hi
Nice machine, the Sisis rotorake came with different selectors, you are showing the verticutter, not just a scarifier, when you set this selection correctly, it will scarify but also slice the roots of the grass allowing the grass sward to re germinate without seeding.
Other selectors include a scarifier and also a brush which can be used on hard weather surfaces as well. There should be also a collecting box which sits on the front like with a cylinder mower.
The Rotorake was introduced in the late 1970’s, and is still made today but with improvements, looking at yours it appears to be mid 1980’s. I have a 1990’s version with a MAG engine, which I use frequently in my buisness, and yes they hold their money, in a word to get a good second hand one, is like looking for rocking horse ******
Just one word of warning, dont use in dry spells and dont over set the selectors as if there are slight lumps in the surface of your lawn, it will grind them out!