Just to clarify, I think Ole is indicating that the C/V 21mm couples to the camera body rangefinder for focusing, not to any known parallax-correcting in-camera viewfinder frames.
Originally Posted by mrcallow
Since all the C/V bodies' accessory shoes are designed to seat auxiliary finders directly "above" the lens, they only need parallax correction in one dimension, up/down for a horizontally oriented shot. So they are simpler in this regard than the typical built-in parallax correction lines for most rangefinder bodies, which have both horizontal and vertical offsets between lens and finder to indicate. All of the C/V accessory finders with bright lines (this excludes at least the 15mm finder) that I have seen have parallax correction marks for 1 meter. Go to the cameraquest.com C/V accessories page on finders for good information on which finders are bright line and which aren't. Gandy's information is pretty comprehensive, including the finder magnification for a number of the finders.
Any of the C/V lenses at 25mm or wider should include an auxiliary finder in the price when ordered new from a dealer.