The Voigtlander 10 mm lens does not come with any manufacturer data regarding the position of the entrance pupil. However, being an extreme wide-angle lens the entrance pupil must be very close to the front of the lens.
Following the method discussed in Measuring The Entrance Pupil, the entrance pupil can easily be determined- see Table 1.
The entrance pupil position from the image plane was determined to by 68.7 mm or 50.7 mm from the flange. On the Roundshot VR Drive with the Really Right Stuff MPR-CL nodal rail, this gives a measurement of 79.2 mm.
For all my panoramas taken with the Voigtlander 10 mm, I set the nodal rail to 79 mm on the Roundshot VR Drive. These images Sheraton Desert Oasis May 2017 were all taken with this setup.
Table 1: Voigtlander 10 mm Lens Entrance Pupil Data