Other Valve disassembly, orings?

I'm trying to disassemble a valve can anyone tell me if the black thingy is an oring or something else? What's the best way to unscrew this thing without gouging or scratching it up? Any more orings inside of it?

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I hope that it's not a special ring, although an O-ring can often be substituted.

Just a general comment because I have no clue about that specific component. O-rings can deteriorate and distort to the dimensions in which they are contained. On the other hand, there are square-shaped O-rings that a hydraulics or other supplier may be able to identify and provide. In my experience, square O-rings are not common. If it were mine, I'd be tempted to try a conventional O-ring to see how it suffices.
 
I hope that it's not a special ring, although an O-ring can often be substituted.

Just a general comment because I have no clue about that specific component. O-rings can deteriorate and distort to the dimensions in which they are contained. On the other hand, there are square-shaped O-rings that a hydraulics or other supplier may be able to identify and provide. In my experience, square O-rings are not common. If it were mine, I'd be tempted to try a conventional O-ring to see how it suffices.
Yeah I'm gonna chance an oring change. They guy that built it retired a while ago.

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