Mystery Button Voigtlander Bessa RF

[Heidi Rosser]

Hi, I'm in the process of fixing up a Voigtlander Bessa RF I was given.
It's still in a bit of a state. I'm trying to work out what the function of a small chrome knob/button is on the top by the framing viewfinder.
Does anyone know what this does?

 

[Dany]

It seems that this small button must be rotated to put in action the reducing mask inside the viewfinder

 

[webestang64]

Found this.......second paragraph......

Photo-Analogue: Voigtländer Bessa RF

 

[Heidi Rosser]

Thanks that helps greatly. I've found the part to make that work too that was in a bag of bits I was given.

Someone gave me the camera and the whole rangefinder had been disabled. I think it's finally doing what it should now.
Just need to complete the final assembly.