I've been looking for months, if not years by now, for an Aland Islands cover for my Peacemaking collection, and I've finally found it!
You may remember that I once showed you a cover sent from Geta to Sweden. You can still see it here. That cover was supposed to show that from the 1920s onwards, after a League of Nations decision, the Islands remained Finnish but that the Swedish language was guaranteed. I knew from the very start that that Geta cover was a feeble part of the collection, so I kept on looking for something better. And here it is:

It has all the evidence I need for abovementioned circumstances: the cover is dated in 1937 so that's not too long after the League of Nations decision, and way before any further major changes took place (such as the Islands issuing their own stamps from 1984 onwards). The card is written in Swedish which more or less shows the Swedish language was prevalent in the Islands. By the way, if anybody knows any Swedish....
Although having said that, with the help of Google Translate I suppose it says something like: you're my best friend.
The card has a Finnish stamp, which shows that the Islands remained part of Finland, and, most importantly: the postmark is bilingual, with the Swedish name Mariehamn at the top and the Finnish name Maarianhamina at the bottom. This shows again that the Swedish language was officially guaranteed.

So now I'm finally happy and can move on to other (though not necessarily better) things!