Brake servo am i missing a seal,

[sneakycorsa]

On the back of the servo the bit that mounts to the master cylinder using the two 13mm nuts, apart from the seal around the push rod, should there be any other seals, only i noticed like a big round deeper section on it & it looks like a rubber washer or some sort of seal should go in it, but dont remember taking one off.....

Any ideas .....

[Edd]

Iirc there's a foam washer type thing, mine fell apart in my hand when stripping it down, can't see it doing much so won't bother re fitting it