This is a dash mirror pad in my MGA. It is black hard plastic and has been there for decades. Maybe not original, as there is no such part in the Service Parts List. I don't remember where the part came from. Maybe I made this piece to solve a paint chipping issue, about the second time I had to repaint the car (possibly in 1998). It is not for anti-vibration, as my mirror does vibrate a road speed (3000-5000 rpm engine speed). It might be a vibration suppressor if it was softer rubber material.

The hard pad is not for anti-vibration, as my mirror does vibrate a road speed (3000-5000 rpm engine speed). It might be a vibration suppressor if it was softer rubber material. Maybe I'll try adding thick rubber grommets underneath. Leaving the screws a little loose might work then, but they may need to be secured with a mild thread adhesive, like Locktite 222 maybe. If the screws are left loose with minimal gap underneath (and the threads glued), then the hard plastic pad may be needed to protect the paint.