VW Golf mk 2 "thing" on driveshaft.

[100SRV]

Per title really, 1986 Mk 2 Golf has a circular rubber thing on the RH driveshaft, doesn't look like a mass damper as there's no significant mass on the outside.
Also it's no longer bonded to the shaft.

Any ideas?

I thought maybe it's protection for shipping a replacement shaft which was never removed before it was fitted.

Here's an artist's image:

[richhead]

It is a mass damper