-SG- I was recently asked if I had one of these by a friend who wanted to make a pattern and cast up one or more for himself. As it happens, I do have one - picked up at a Banbury Run autojumble many years back. It is quite a robust casting - see photos - but there do not seem to be many bikes around still wearing them and I suggest the reason is simply that they will ONLY fit the ML CMAK magneto which was fitted to all diamond framed Nortons (those supplied without magdynos, that is) during '29 and part of '30. If for some reason, the magneto had to be changed for another type, then the old cover perhaps got put in the shed and eventually thrown out! It is secured to the magneto by a single nut which locates on a stud extension of the ML earthing brush holder. I made up a knurled nut to fit my particular magneto/cover but I do not know if this was how they were secured originally.