Originally Posted by
bikemig
I'm familiar with the Simplex dropouts. Peugeot used them in the 80s. I have one on my 1982 Peugeot PXN 10. It's a good drop out that works with campy derailleurs as well. The dropout on the Sekine is different. It is not threaded. I think the purpose is just to provide a stop so you can center the wheel. First time I've seen one like this that was manufactured as part of the drop out.
The Simplex dropout isn't threaded, either; that's the purpose of the threaded plastic insert. Is there a similar hole on the non-drive side dropout?