I checked all functions with my Super Nintendo connected...
It responds to all front controls (brightness/contrast/vertical/horizontal). After a few minutes, it start losing vertical deflection at the bottom.
With Nintendo connected, I can tune in Channel 3 and get great sound, but no picture at all, just noise on the screen. The screen is completely different with Nintendo on or Nintendo off, so it does "something" when Nintendo is turned on.
There are also a couple of black dirt spots on the screen, looks like physical dirt that will need cleaning.
Here is a photo of dark bottom and dirt spots:
https://photos.app.goo.gl/1tjHUWYjz6DSTA5S9
I can borrow my parents' VCR for another quick test, but not sure if it is worth doing that.