Well if i'm correct it's mostly 15th century, and I have a mid-15th century kit already (I wore it to VARF sans sallet last year).
Well if my memory serves me coorectly, we do have evidence of reenforced collars in the 13th and 14th centuries as well, though they were most often of metal or whalebone construction. Mine's more a historical plausability than anything truly typical in those centuries.
My main promting is actually something to wear to give a more complete look to my harness when wearing it without a helm. It never fails that some punk kid has to point out that "He could easily defeat/kill me by targeting my neck, which means that knights obviously sucks....ect ect ect." And it gets annoying to explain what an aventaille or bevor is over and over again, so I built this, to shut them up. So that's my explaination for wearing it in the 14th century.