Sweden sold off Swedish Pomerania at the end of the Napoleonic wars in a good piece of business. Initially they wanted to swap it for Norway with Denmark, but a

Sweden sold off Swedish Pomerania at the end of the Napoleonic wars in a good piece of business. Initially they wanted to swap it for Norway with Denmark, but as the Norwegians balked they never handed it over and then the Prussians swooped in and bought that and other bits and pieces off Sweden and Denmark. It was a good piece of business as the defense of it would have cost resources but it still would have been a walkover against a serious opponent. And they would have lost it soon enough, at the latest in 1848 and the upheaval then.