The hub says “Shimano 600” in the identifying ring and after that it has the tricolor green/light blue/dark blue band. It is 126mm between axle nuts so it isn't an 8 speed or more. What is different about this freehub compared to all the 6 speed Dura Ace hubs I used to equip on bicycles is that one of the splines is narrower and one valley between splines is wider. That is visible in the picture. Original 6 speed cogs will still fit on it just fine. The threading for the screw on cogs is larger in diameter than Dura Ace and longer as well which is why I think it needs 2 thread-on cogs. I’m sure I bought those screw on cogs (13 & 14) at the same time I bought the hub realizing I couldn’t use Dura Ace screw-on cogs. They have a built in spacer that is narrower (slimmer) than older 6sp screw on cogs. So my logical assumption is that this hub is from the 7sp era. The reason I’m not as familiar with Shimano 7sp freehubs is that I often liked to use Campy or Shimano large flange hubs matched with Shimano 7sp freewheels. My dilemma now is finding the right spacers to go with all the 6sp cogs I still have in stock.

I built this wheel to go on a frame I made as an example of how to build a frame in one of my framebuilding classes. I would describe this bicycle when it is finished as a “go for a walk” kind of bicycle. In other words something I can pop on and go for a short ride in normal clothes and shoes without the need to get all kitted out. Our city just finished the last section of a bike trail that is now very near my house and shop. I’m going to equip it with stuff taken off of frames I repainted and put new parts on. It is going to have upright handlebars with Suntour friction shifters. Around the triple front crank will be a chain guard to keep my jeans from getting tangled into the rings or chain. It is a lighter version of the internally geared bicycles we provide for pastors in Ukraine. Once I get the wheels sorted out I’ll need more advice on which old derailleurs to use that came off of bikes I’ve repainted.