This is a simple adapter for the Wild M400. It bolts onto the for holes in the top plate. It has a smooth 46mm inner diameter which accepts standard M42 spacers with a hole to accept a bolt to act as a set screw. This allows you to rotate the camera as needed.
Use it with inexpensive M42 spacers, an m42-m42 helicoid and an m42 adapter for your aps-c camera of choice.