You're probably going to be the man I come to for the future. Are you selling any of these cogs by chance?
And did you mean that the Dura Ace and 600 cogs are the same? So does that imply the bodies are pretty similar as well?
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70's Nuovo Record Jeunet Franche Compte, '88 105 Trek 1200, '85 Victory Bianchi Vittoria, '89 Exage Bianchi Strada LX, & '11 Shimano Masi Partenza