Description from camera-wiki: "Rada made rollfilm holders (film backs) fitted with a dark slide, designed as adapters to use 120/620 rollfilm  with 9x12  plate cameras, resulting in a 6x9 image (or smaller with mask inserts for 6x6 and 6x4.5 formats). 
The most common multi-format holders use dual red windows and insertable format masks (the latter frequently missing from holders bought used). 
The left window is for use with the 6x6 mask; the right window for 6x9, counting only the odd numbers on the film's paper backing, or all numbers with the 6x4.5 mask.
Manufactured in the 1920s to 1960s (perhaps into the 1970s) by the German manufacturer Rada, a Plaubel subsidiary."
 
In great working condition.
We have fully tested the mechanism with a dummy film (not included), and all works smoothly as it should.
An instruction manual is available here: https://butkus.org/chinon/rada_rollfilm/rada_rollfilm.htm
or you can upload it from the Product Documents attached in this listing.
 
PLEASE NOTE: The mask inserts for 6x6 and 6x4.5 formats ARE MISSING!