As the subject says - anyone know when they began milling windows in the nosecap sight ears?

I've got a very late 1944 Lithgowicon, not refurb marked, with early 1945 dated furniture - probably a december 44 receiver assembed in 45 at Orange since the the but cartouches are OA Orange, not MA Lithgow.

The nosecap has the windows mileld into it and for the life of me, I can;t remember when they started doing that - pre or post 1944?
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