Questions about Kunzing Type Pugio

[ioannes sebald]

When it comes to this particular topic,i always end up with several different opinions from various people,so,i am rather keen on narrowing down the following range of dates for this weapons usage and i wondered if anyone could tell me,a) When was the latest probable date for its appearence in the Roman military (in the west of the Empire) and,b) After it was officially abandoned,what were the chances of individual soldiers retaining theirs?,and if so,for how long might they have done so?,a couple of odd questions,perhaps,but i really need to sort this out satisfactoraly and any feedback would be most welcome .