On December 10, 2021, Serbia issued an unexpected souvenir sheet at the occasion of the 25th anniversary of the relationship with Kazakhstan. Stamps represent the two capital cities, Nursultan and Belgrade, and the souvenir sheet has a shape ideal to be produced as a joint issue. Unfortunately, no information is available from Kazakhstan so far. There is a high risk that this issue, probably initially planned as joint, will remain an unilateral product.
A similar situation may take place with Austria, which issued on December 6, 2021 a souvenir sheet also designed like a joint issue. This product initially planned to be released in June 2021 was somehow announced as potential joint issue with Greenland. As for the previous product, this souvenir sheet may remain unilateral, as no information is available from Greenland so far.