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The rubber grip slides off easily if you lift it with a flat screwdriver.
You will see a total of four screws exposed immediately.
Two plain slotted with a nylon washer need a 3mm screwdriver (any smaller and it chews up the screws
Remove them and then you can unscrew the entire front assembly. Takes maybe 4 full turns or so? Be sure to set the focus to infinity, and when the front comes off, mark both parts to remember the correct alignment. The helicoid has multiple parallel threads, so if you don't get the right thread then your lens won't focus to infinity (it'll be way off, so you will notice the mistake, trust me
Now you can already clean some parts of the lens.
If, like me, you need to take the focussing cylinder out then you have to unscrew the Philips (cross) screws just a little bit. They hold a small plate the stops the lens from focussing past infinity. If you slide it upwards you can also unscrew the focussing cylinder, which takes a lot of turns! Do NOT remove the screws completely, there's no need for that.
Not sure if there are multiple threads there, but be sure to mark out the final orientation (i.e. what it looks like before disassembly).