Okay, so it took a little longer, but here's that Swiss cover I told you about in my last post.
As you can see, the stamp was cancelled with an ordinary Yverdon date cancel, on 16 August 1919. And this is the special airmail cancel on the back:
I've also seen them in French and I suppose there might well be an Italian version too, but I haven't come across one of those. I believe the fourth official Swiss language, Romansh, was normally never used for things like this. Whenever the Swiss did issue multi-langual stamp sets (or postal stationery), it was, as far as I know, always in German, French and Italian. But do prove me wrong if you can!