The NJS stamped 17t Dura Ace cog is the holy grail of hen's teeth.
Some doubt it's existence, others claim to have owned several 'back in the day' before riding fixed was cool, few speak of a shady conspiracy and back handed pay offs from tyre manufacturers to have the only prime number toothed cog in the DA range that gives a rideable street gear taken out of production.
I think you mean suntour