Roberts, my undestanding is that all wharncliffe knives are from the remodeling on, just like the run-of-the-mill-MP 600 series ( this, because the ST and the the Snap On models , like Cody said, have always come with a sturdier knife blade). Remember that the 400 and 600 series share the same internal tools so, I'd guess they've been like that since close to 2008 (IIRMC), when the MP 600 logo got replaced and the tool revised.