Unfortunately, it looks as if Leica would have a dodge around the argument that the Kalart magnifier (and the assorted eyepiece magnifiers offered for SLRs since at least the late 1950s) constitute "prior art."
Their patent text spends a lot of time describing the benefits of magnifying the image of a combined range/viewfinder, noting that this would provide not only greater focusing accuracy but a larger viewing image when using small frame sizes.
So, they could claim that their patent applies specifically to an eyepiece magnifier for a camera with a combined range/viewfinder, whereas the Kalart device is for the rangefinder only, and the SLR magnifiers were for SLRs.
Which, to the average man on the street, would be an outrageous scam, since the whole idea of patents is supposed to be to protect inventions, not just slightly different uses of things that already exist and are well-established. To said Joe Average, it would be outrageous to think that you could build a gizmo and have it be "innovative" when held up to the eyepiece of one kind of camera, but a "patent infringement" when held up to the eyepiece of a slightly different kind of camera, when it's the exact same gizmo!
This is what I was thinking in my earlier post, when I speculated about obtaining a patent for some well-established device based on thinking up a slightly different USE for the device. For example, how about a patent application for "Apparatus for Securely Deleting Data from Flash Memory Devices," comprising "(1) a roughly cylindrical part having a weight roughly in the range of 1 lb - 10 lb and composed of iron, steel, or other heavy metal and formed so as to be capable of sustaining repeated impacts; and (2) a tubular or oval-shaped part affixed to the first part at a right angle, having a length of approx. 10 - 36 inches and composed of wood, fiberglass, or other rigid material, formed so as to provide a handle by which the first part may be swung to generate impacts, for the purpose of reducing the physical structure of the flash memory device to a non-readable form."
Wouldn't it be obvious to anyone except a patent examiner that I was trying to obtain a patent on the sledgehammer, and that it would be silly to grant such a patent merely on the grounds that I was proposing it be used to smack memory cards rather than spikes, chisels, posts, thumbs, and all the other things sledgehammers have been used to smack since approximately the dawn of history?