I have an empty steel CO2 cylinder that came with a kegerator. Going by the size it's a 5 pounder. It is old and I'm pretty sure it needs a hydro test. My nearest fill station (GTS in Conshohocken) charges an extra $10 for this when swapping.
Since I already have a couple cylinders I'm pretty happy to let this go. Ideally I'd like a local trade or part exchange (I'm in Narberth, just outside Philly). Amongst other things I could use shanks and a Sanke D coupler. I could ship it but I think FedEx would charge about $20.
The stamps on it say:
and on the other side
The label says BOC group.
Edit: here are pics of the stamps.