Another brush you are not likely to see come around too often, but I thought some may enjoy learning about it anyway. This is a Wold Model U. Dating back to the early part of the last century, the design and function of the brush is quite unique. I had read that the brush was difficult to control, but with so few samples floating around, I could only go by what I read... What makes the brush unique, is that the trigger is unlike most other double action brushes. It is divided into two levers, one within the other. When you depress the main button, the first part of the movement initiates air flow. As you continue to depress the button, it makes contact with the second lever. The downward movement of the second lever forces the needle back, thus initiating paint flow. The further you depress the trigger the further the needle is pushed backward. There is also a small thumb screw in the back of the trigger lever arrangement that allows the user to pre-set the needle draw for fixed line width(s) upon air initiation. This brush was not working when it arrived, but was an easy enough puzzle to sort out. Unlike many of the reports I have read about this brush, I don't think it is terribly hard to control. It reminds me a lot of the fixed double action brushes of Europe - like the Grafo, Hansa, and Efbe. Instead of the action working while the trigger is drawn backward, it works while the trigger is being pressed down. If you have good hand/eye co-ordination, you would have no trouble working the action - once you become accustomed to it. I am thrilled to have added this one to my collection. It really is a wonderful piece.