Thanks for the comments
I was surprised that every screw was a flat head, don't know the right term, the opposite to the philips or JIS
I do not own nice and small enough flat screwdrivers, but tried with my jewelers set and it worked
All the screws were rather loose, I guess the lens was serviced in the past
The aperture ring had some sand underneath, now clean and with new grease it moves smoothly and clicks are precise
I did not venture into the focus helicoid, which I wanted to do , but the screws are tiny and my screwdrivers are not good enough, time to pay a visit to the tools shop where I got my JIS set.
The aperture spring got undone, and I was worried the ball bearings may get undone, which gladly did not happen
I did read Richard's blog about the 55mm repair, and AI conversion, since I do not own a support for the dremel that moves, his suggestion to control the depth of the cut of the dremel using a magazine was quite useful