How do I get these off?
The little concave inner bits like the ones on these shifters:
How do I remove these from my braze-ons?
With gentle persuasion from a flat-bladed screwdriver between the frame and the concave 'washer'. Remove shifters first and protect frame with a samll piece of thin plastic (bottle)
First. I'll assume you've removed the lever fixing bolts and the levers themselves.
The backing plates (that's what those curved inner pieces are called) have square holes that are just a friction fit on the braze-on lugs so they should remove fairly easily. Have you tried just to pull them straight off by hand? They usually come off that way without too much effort.
Otherwise you can pry them off with a small screwdriver or knife blade between the frame and their inside edges. Be careful not to gouge them or scratch the frame.