That's really cool. From pics, I always thought that was wood.here's a better pic. it's a copper spring to which felt pads were attached for muting. since each one's independent on top by way of the slits they could be raised or lowered independently to taste. the bridge cover would have concealed all of this. although i don't like how it looks (and don't use it) i keep it on (it's held down by the two point screws) so as not to lose it. saw one on ebay going for 290.00 recently..
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