Is that like cork or what?
I’m repairing a M40 but top gasket thickness ?
It's a paper gasket, probably 0.5mm or somewhere close to that. It's ot that serious on a M40 if it is thick or thin.
The M40's and M41's that I have worked on all had the cork type gasket, relatively thin, 0.5 to 1mm, but as Roinik says, not a problem, just make sure you don't use 3mm cork sheet from Supercheap / Autobarn, since that will reduce the tension on your indent springs.
Looks to me like it's cork. And pretty cheap.
https://vp-autoparts.com/en/artiklar/gasket-gear-box-lid-m30-40-41-400-410.html
Just got home and measured the thickness of the cork gasket in question, it is actually 1.5 mm thick.
Thank you guys for the replies as I have closed off the top of the gearbox and it feels just fine.
As the gear lever is the sort one I will have to grease the connection steel to steel and then put it in.
I will have to get some help with posting some pictures,maybe some time later.