I would remove the pads and check for the contaminant. You might get rid of it when you take the pads out. You can give it a proper inspection then. It might be something stuck on the pads?
Hi and welcome along buddy. They're great cars. The 67 plate is where the lower tax bracket came in iirc. From 2014 onwards they had sorted out the galley gasket issue also iirc. good luck in your search.
Hi and welcome along buddy. The best thing to do is go and test drive a few as Glen said even if you have no intention of buying them. I love the roadsters. I've had a 350Z roadster and I now have a 370z roadster. They're great cars.