Here, the head is stretched over a cast "tone ring" which imparts a clear ringing tone with a good range and balance. It's easy to spot because the head is flat all the way to the edge.
The other major style is known as the "raised head" or "arch top"
This one has a tone ring with an inner raised portion over which the head makes a bend downward toward the edge. Because the vibrating surface of the head is an inch and a half less in diameter, this banjo has a higher natural pitch. The instrument then has greater power in the high registers, and less strength in the bass region. Raised head banjos have less sustain and a more percussive tone.
Here's a flathead resonator banjo with a clear head:
You can see the large cast tone ring sitting on top of the 3/4 inch thick wooden shell.
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