The old spheres had a simple date code like 28-03-07.
However the ones fitted to my old car about 4 years ago have no obvious date code.

They have the correct Citroen part number and are embossed with a double chevron.
The are stamped with a '40' which is probably the pressure in bars.

Is there a guide to de-coding the time of manufacture of spheres?

Hi Brendan

As I understand it late on in the XM production Citroen introduced a new type of membrane for spheres.
This replaced the previous two types used for different service applications.
The new composite membrane is much less likely to rupture or loose pressure.
Green coloured spheres have membrane marking as well as age information.
Then Citroen decided to paint spheres with the new membrane grey.
Been a long time since I saw this info and no idea where, sorry.
I pressure test speres for reuse and do not worry about age or membrane type.

John

Thanks xmexclusive,

The spheres I fitted yesterday were grey and the ride seems to have improved.