Zanussi Jetsystem 1200 RSI (FJ1296) Brown spots on washing?

My Zanussi Jetsystem 1200 RSI (FJ1296) is leaving brown spots on the washing. It almost looks like an iron mark as it is a brown pattern of the holes in the washing machine drum. So the clothes which are touching the drum get these marks on them.

Any ideas? It was clanking a bit recently and now I'm thinking that maybe a coin or something has slipped inside and gone rusty????

How do I take it apart and fix it - any tips?

THANKS!