That I don't know, either. Although I do know that even the little M6-751 collets made for the Atlas 6" lathes have a key. I don't have any R8 collets here to look at but many many years ago, I bought a round-column import mill from Enco to use for machining artificial defects into line pipe in our pull-test facility. Someone managed to shear off the alignment key and I bought a replacement quill. Around the same time, we were bought out by our worst enemy. The new quill never got installed and ended up in my shop. I just looked at it and it definitely has a key. Unfortunately, the odds against it being the same as yours are probably huge.