The angle of acceptance is over 80 degrees and a simple frame finder is fitted instead of an optical viewfinder.  

If the camera is used with plates, the viewing screen can be used but, with such a wide angle lens and fixed focus, the screen is of little benefit.

The film transport cradle with rollers can be removed by lifting the winder knob and the back with pressure plate replaced by focusing screen or dark slide.

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File source: 
https://www.photomemorabilia.co.uk/Ilford/Envoy_WA.html