Stu,
Take a look at the milling on this "N" marked frt sight on my S'G' 1,823,135. It shows a similiar fingernail milling style like we find on Win Type I's.



The milling pattern is probably just from the person doing the milling, but the side profile looks very close to Winchester's profile. Below is a picture of a normal Winchester type I,



Regards
Charlie-painter777