While I can't speak for sure of the historical accuracy of your particular gorget, Tim at Red Falcon Armories (who made my leg armor and will be making the rest of my 14th century kit when I get the money together) has told me that brigandine style gorgets appeared sometime shortly after the brigandine body armor. According to him they remained popular well into the 17th century due to their relatively good protection value vs. weight and movement restriction. The style that he makes is more similiar to my brig body armor, steel plates covered with leather on the inside and outside, the plates are smaller rectangular plates, not the larger ones like your gorget has. We had a brief discussion on gorgets since I am working on 16th century padded armor to be worn in conjunction with a gorget and possibly pauldrons. I was slightly shocked when he suggested a brig style gorget would be more appropriate for me than a plate style. According to him, most soldiers wore brig. styles, only wealthier officers wore plate style and those were most commonly worn only on ceremonial armor or for ceremonies as a symbol of rank.. In battle, the preference, according to him, seems to be for brig styles. I am not sure where he got his information, but as a professional armorer I would tend to trust his opinion, especially since I have seen him refer people to other armorers for styles of armor that he isn't particularly familiar with or good at making. I think that this brings up an interesting point though, the effigies studied may not reflect the actual battlefield look or armor worn by the various knights. Also, these do not necessarily depict what is worn for those of us looking to portray a common soldier. As has been said before, a lack of depiction or mention in sources does not necessarily mean that the item in question can be ruled out, rather it may be that it was assumed to be common knowledge and thus not worth mentioning.