I could be wrong here, but it looks like a SA cylinder that is powered in RETRACT only.
IMO, that really limits what you can do with it. If it were a push/extend under power cylinder, I would probabally hold on to it.
With that said, I think I would sell it. It doesnt appear that the rod is in great shape anyway, and probabally will either drip/leak, or need rebuilt soon. And who knows about the pump unit. I would probabally hold onto that IF it is 12v and works. That way, if you ever have the need, you already have the powersource, because those things run $500+ new. But the cylinder, odds are it wont be the right size anyway IF and WHEN you ever have a need for one.