Chosen Solution

As my top glass on the Apple Watch 3 broke, I ordered a new digitizer. When I removed the glass from the display, I damaged a black foil on the OLED display at the edges. The display is still working, but there are bright areas, where the foil is missing. What kind of foil is on the display? Can I replace it? Where to buy? Update (01/06/2019) The display looks like this now (glass removed, dark foil damaged):

Its polarizer film. And for the apple watch it is very dark in contrast. Done plenty using the warming burner on my stove with laptop tape. Perfect removal everytime. I would suggest using Samsung’s polarizer sheet as a replacement. Trim to fit and use loca glue to attach and loca for

While I know you don’t want to hear it… I would just replace the full display assembly Apple Watch (38 mm Series 2) Screen or Apple Watch (42 mm Series 2) Screen

When the you removed black film, did you damage the gold foil in-between the polarizing film and LED display?