Brooks Veriwide XL back question

[x-ray]

My sweet wife is giving me a Brooks Veriwide for Christmas. It's the model with the interchangeable backs. The back that comes with it is the original type with 4 pins that mounts directly to the body and does not need a Graflok adapter and was made by Mamiya.

She purchased it through the mail and everything seems to be in order. The 47mm SA f8 is perfect and the shutter accurate. The original VF is very good as well. The body and back look almost new.

Like any new camera I check them out carefully. I ran a roll of 120 through the back and marked the frames with a pen to check spacing and it's excellent.

Now the question, the back takes both 120 and 220. I ran a roll through it and it must be set on 220 because it still advanced frames at the end of 8 exposures, the end of the roll. How do I set the back for 120 / 8 exposures? There's a 120/220 reminder on the top but I see no way to switch between 120 and 220.

 

[sevo]

On Mamiya backs you twist the film sensitivity reminder on the left hand side (right next to the film length and frame counter windows) to switch between film lengths. But even if that Brooks back should really be Mamiya made, it probably has little or no technical relationship to the Mamiya Press backs - it is B-shaped, not S-shaped, and the transport lever is on top of some things not present on a Mamiya back, on the wrong (left from the rear) side, where the counter mechanism would be on the (right hand winding) Mamiya backs.