This spike came in a box of junk well over 25 years ago and I dismissed it as fake, until three dealers saw it and expressed interest - without telling me just why. Looking at it again it is remarkably well made of 'spun' aluminium, three piece construction swaged together, 5 vent holes, non removable tip, 77mm diam. base plate, total height 86mm and, of course, as light as a feather. The colour is patinated to a really good match to the field gray of M15's and I now wonder if it was part of some kind of private purchase lightweight M15? IF it is a fake someone went to great lengths to do a very good job of it.
Steve