Thanks for advice!
On the pants on the Yoox picture the buttonhole is in place. And on mine there was a tag with a handwritten size note.
They seem like washed wool - 100% wool, very thin and "undense", yet quite substantial and heavy, not flimsy, and a bit itchy. I wish it was a complete suit.
Putting a loop would not be a good idea?
Can these be worn in heat? The fabric is very breathable both ways.