That's great - are the bolt sleeves exactly 12mm? The OEM sleeves from the battered coupling I removed from an early SADS are 12.00mm. The smaller of the sleeves on the Febest couplings I got were 12.5 or so. Also, the stock ones have a .5mm chamfer on the end, and the Febest part's sleeves don't.

I bought a pair of similar couplings on ebay three or four years ago that I rebuilt an early shaft with, and they worked fine. I don't remember if there was a brand name on them at all though. Guess I got lucky.