Originally Posted by
JohnDThompson
I haven't seen that particular dropout before, but Simplex made a similar one. The hole was to hold a threaded plastic insert through which the adjuster bolt was inserted. If there's a similar hole on the non-drive side dropout, that's likely its purpose.
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.