Could be a quarter turn valve so it only turns one way. Ballofix are like this. Sometimes the shank that you turn to open/isolate will protude further than others and will generally be more a rectangular shape.
They are pony , proper full bore are the way to go. , times i've seem this carp fitted to cold feed cylinders , cold down services , main supplies , not forgetting the PTFE wrapped around threads/olive.
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