The 1”wide trim/casing strips around my 1968GT Philips/Corning windows were factory applied in a rail/stile fashion, where the corners were not mitered, they're lapped over each other.
The material and workmanship is cheap and sloppy. It is a thin, perhaps 0.020 ribbon of wall matching vinyl weave covered 5052ish aluminum. The trim is thinner gauge aluminum than the walls. It's junk, affixed with 1/8” pop rivets.
I'll guess that the less than mediocre workmanship/design is poor because the designers/fabricators assumed that most of the window casing would be hidden by curtains.
Someday I will remove it all and re-case the windows with perhaps 3/4” x 1/8” mill finish aluminum strips.
The images are of the original trim/casing as installed in October,
1967, and of a removed strip where you can see that it has about a 20degree transition bend along both its edges.
I got lucky and didn't need any trim around my kitchen window when I back-splashed my kitchen walls.