A hatter´s tool

We have found something that we have been searching for since quite a long time. It is a hatter´s tool, used when making hats and constructed so that the width is easily adjustable. In Swedish this is called a "hattstock". If anyone reading this could help me with the correct English/American name for this tool I would be most grateful, please leave a comment.

We are not planning to make hats. We will be using it blocking knitted hats and caps. A great plus is that it is old, handmade and have a fantastic patina from many years of use. I feel respect handling, using  and caring for an old tool like this. I wish it could tell us its story.