Those M705s are NOT identical. There're two main versions. The original 2010 intruduced one had another key you activate with your thumb to show up all open programs on the screen. The new ones after 2017 lack that feature. They are VERY easy to keep appart. The one pictured here is the original 2010 verison. Look at the little rice corn shaped dot where your thumb is rested. Thats the version with the discontinued side key. HIGHLY prefered to the 2017 version imho.

Because I already owned the same mouse before and I was very satisfied with it. And the few francs difference compared to other mice is also not an issue over the long usage period. Happy new year.