There's been a lot of No.4Mk1's reworked into No.5's by several importers lately. I've read several reports stating that the wandering zero was a bogus story put out by a high up in the British military to make it ease to go with a semi auto in 7.62mm Nato to get with the mandated program just after WWII? Instead of trying to convert so many No4's to the Nato 7.62mm, which doesn't work well, by the way. I've shot several and never experienced the wandering zero in any. You can verify that it is an origianl by taking it out of the stock and checking for the lightening cuts made on the receivering? I currently own one of the fakes and to my surprise, it shoots very well. of course, the main problem with the jungle carbines is the recoil they generate compared to the full rifles? Hard but not unmanagable.