2011.01.25. WMIL - Wikipedia 10th Anniversary Commemorative Postmark
25 January 2011. On behalf of Wikimedia Israel, Israel Post (the Israeli monopoly postal service) will be stamping all items passing through several major post offices in Tel Aviv and in Haifa with a special Wikipedia 10th Anniversary postmark.
In addition to the anniversary, a second special postmark will be stamped on all through Wikimania 2011, in August!
To the best of our knowledge, this is the first time Wikipedia is featured on postal materials.
This cool way of marking the anniversary is the work of Wikimedia Israel member Liron Dorfman, who's done excellent outreach work with Israel Post.