Vincenzo Capriotti

Hi, I recently bought an Arri SRII. It's the first time I'm using this camera, but it looks like it was converted, so it now mounts a 35mm eyepiece taken from an Arri BL4. My problem is, the eyepiece is on the right side, and I'm having troubles trying to make it face the left side. How does the unmount mechanism of the camera work? It seems completely stuck.