Had a quick look at the 737 SRM this morning (06:15!) Whilst there are standard repairs for cracks eminating from some of the window corners there isn’t one for the area shown on J.T’s 707. BUT…… on the 737-3/4/500’s there is an 1/8″ doubler of almost the same shape on the inside of the skin! My guess is that there was a comon problem on the 707’s with cracking in that area and they beefed up the 737 structure to prevent it.
I wonder if the same area on the other side of the aircraft has that repair aswell?

Rgds Cking