I have NO idea, BUT, if this William fox died in 1769, he would have been about 45 as he passed (being 15 as-freed in your estimation). It would seem he worked from way before 1780. Therein lies experience in the style of the razor, educated guess at it's original configuration. Things which suggest a 'period' to place it in. I do know that before early 1800's things seem to get sketchy from what I read of other's research. In that regard, it could very well be what you want it to be until you find something which steers you another direction. I have a few like that!