Thanks for your answers and discussion! I wanted to write a question mark at the end of title, not an exclamation mark, my bad
I didn't realize that pedal threaded part is pretty much the same give or take a 1 mm or so. All my other cranksets are thinner, so this looked so weird to my eyes.
I also now realize that I was using SPD-SL as a generic term for all the type of cleats like Shimano, Look Keo, Look Delta etc. Lesson learned.
The pedals are indeed Look (or by Look patent) Campagnolo, made in France.
The pedals are now installed without the washers.