Thanks Lauren, I saw the info about the two rivers here on the forum. I was a bit worried to ruin the padlock, but followed your suggestion and did it...
I'm very happy I disassembled the padlock. Now I have a working key. During my previous attempts I impressioned correctly the first and fourth levers, but filed the second and third too much.
I started over with the last piece of brass I had, and filed carefully.
One thing I noticed is that the uncut side of the blank interfere with the lever positions. I suspect I screw up the previous attempts because of this.
I took many pictures and will make a topic dedicated to this beautiful padlock. For now here is a picture of the working key, it's the first one.
I noticed there is the number 858 punched inside the lock. Dunno if it's the model number or if it's the bittings code.
Cheers