Please could someone tell me what this device is? It was fitted to an elderly Audi model fitted with a V8 possibly a 100 model??

Thanks

The infamous “UFO” brake rotor. The caliper grabs on the inside, offering a much bigger rotor surface area - in theory. In practice they suck! Prone to warping and very expensive to replace ($250 each on ebay) and difficult to find someone capable or resurfacing the darn thing. These were primarily found on the early V8 Quattro models and the 1991 20V turbo 200 Quattro. Many owners chose to replace them with parts from the conventional 10V turbo models.

It's called the UFO brakes, the Caliper is mounted inside the rotor, effectively giving a larger swept area for better braking. Google is your friend.

edit: Doh, too late, he described it better anyway

Thank you both for your reply!
A very interesting device