What is this damper cartridge?

[black lightning 1987]

I think the fork I am working on would have originally had an elastomer. Wondering if this was a mod/upgrade. There isn't a whole lot of resistance when moving it in either direction. I found a cut O ring inside the steerer tube after removal. Guessing about 3/16" in section and 7/8" in diameter. No idea where it originally resided. Any advise on rebuild/replace appreciated.

 

[Nico]

That looks like a sort of DD2 cartridge that has a lock up option.
It should have some oil in it, but not fully filled I think.

It is for damping only, the 'spring' action is done by the elastomer

Edit
Found this by coincidence.
Youtube video

 

[black lightning 1987]

Thanks. It's from a 1999 XS800, has lock out and coil spring/elastomer. Seems to me that the earlier catalogs had more information on the dampers - even upgrades.