Threaded Beer Keg

[Amber Gold]

I bought some Sanke style beer kegs and all but one are the kind with the snap ring which holds the valve of the keg in. One of them, the valve piece is threaded into the keg collar. I've unthreaded the valve, but there's some kind of catch/release/something that's keeping the valve from coming out. Does anyone know what the trick/tool is to get this out?

Thanks

[jmayerl]

Holy old thread but I just got one of the threaded and finally got the stem out. What did you use to cap the keg with now?