Quite an interesting mystery! We all know that, officially, the fastest Canon 35mm lens in LTM was an f/1.5, not f/1.4, and of course that lens looks somewhat different from the one pictured -- for one thing, it has no infinity lock, and for another, the focusing ring is more deeply scalloped, as seen in this picture from the Canon Camera Museum website:
So what DO we have there? Well, it strikes me as odd that the lister never shows us a straightforward clear picture of the lens with all its markings: the photo of the front rim is blurry and the focal length and aperture markings are in shadow; the side view, showing the f/1.4 marking on the aperture ring, was taken with a fisheye lens so it's difficult to judge the proportions of the lens barrel.
The style of lettering on the aperture ring, and the design of the infinity lock and knurling, look exactly like those of the 50mm f/1.4 lens... and yet, in the front view, the front element is smaller than that of the 50/1.4; it does look much more like the front of the 35/1.5. And again in the side view, the infrared focusing mark is not in the right place for a 50/1.4, where the mark would be between the f/5.6 and f/8 positions; it IS in the correct place for a 35mm lens, as you can see by comparing the "R" mark position to that of the lens pictured above.
So, we've either got a 35/1.5 lens on which someone has added (either mechanically or digitally) a 50/1.4-style infinity lock and aperture ring... or else some little-known prototype lens that's not shown in the Dechert book, or on the Canon Camera Museum website! (I couldn't check Peter Kitchingman's Canon lens website as his site is still down.)
If you find out more, please post!!