Thanks 28c! I did find out about some other brakes I have, like the Dura Ace AX's and the Marinovative Decelerators, but not the brakes I have in the picture.
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OK, my curiosity got the best of me. I went and wiped the crud off the brake to find they are..

Scott SuperBrakes!

What vintage are they? 80's? 90's?
The previous owner said he'd had the bike for more than 20 years and he had the brakes changed 10-15 years ago.