I would think the F1 was just what they labeled a crossing, but this is getting out of my league with naming .
These seeds should be labeled Cephalotus 'Eden Black' x 'Eden Black' (crossing 2 seperate plants) or just Cephalotus 'Eden Black' x (Selfing a single plant). Later, if they started showing unique characteristics you could go with "Cephalotus ('Eden Black' x 'Eden Black') New Plant Name Here"
Keep records of everything and keep them labeled very well, that will help more than anything with the value. Even if they turn out looking just like a typical Cephalotus as long as they are properly labeled and can be validated they will be worth way more than a typical.
Good luck with the seeds, hope they grow well.