The one end unscrews and then can be screwed onto the other end to provide additional length while in use. A generous gift from a friend and one that I’m pleased to add to the collection. I need to find a nib that fits but it is otherwise in near perfect condition. Research suggests that this is an example of a “Wise” pen dating to approx. 1810-1830. The 4th image is of another Wise pen owned by a UK expert and author.