Shock Question

[rfpotter]

In cleaning up a Six Days, when I took the spring off the shock and gave it a good cleaning I noticed it is stamped "Girling 7005".
From reading the Production Years chronology, it mentions Girlings on '73's, and since I believe the bike to be a late'72/early'73 this would make sense.
Would this be a model that was placed on at the factory?
Is it an "early" upgrade? Any other knowledge of this type of shock?

Thanks in advance,
Patrick Houston