Hi there. I'm new to enlarging and wanted to upgrade my lens. I'm just using a Besseler Cadet II I got for cheap. I was able to get the lens off. It doesn't use boards and wasn't meant to be exchangeable but it wasn't too bad to get the retaining ring off. Is the 'older style' the 39mm thread? If so I guess I'm interested in one of the 50mm older styles.