This is probably a pretty basic question, but I'm not proud.
My old house built in the 1920s has an updated 200 amp breaker panel. Some circuits are still wired with the original flexible metallic conduit containing two fabric covered wires. Other circuits (kitchen, bathroom, and garage) have been replaced with three wire ROMEX®.
The only ground I see for the panel box is a braided wire running from the bottom of the panel to a clamp on the water entrance pipe about three feet away from the panel.
Is this an appropriate ground? All of the ROMEX® circuits and most of the circuits with metallic conduit read as grounded when I check them with a tester.