V8 Rocker Cover Gasket

[krusty]

How can I tell if it's Cork or Rubber without taking it apart??? As you can see, they look the same.
Oh, I've an '85 90 and I thought I'd treat it to some engine work

http://cgi.ebay.co.uk/Land-Rover-Rang

http://cgi.ebay.co.uk/Land-Rover-Rang

[GreenV8S]

The rubber ones are black; you can see the edge of the gasket sticking out at the bottom of the rocker cover.