It is an Uniglide cassette where the last sprocket is also a lockring. You need to use a chain whip and by the looks of your photo, someone replaced the last sprocket by an actual lockring.
Do you even Sheldon Brown, bro ?
http://sheldonbrown.com/k7.html
@Vince started
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It is an Uniglide cassette where the last sprocket is also a lockring.
You need to use a chain whip and by the looks of your photo, someone replaced the last sprocket by an actual lockring.
Do you even Sheldon Brown, bro ?
http://sheldonbrown.com/k7.html