Here is the tiny bit that I know, none of which I've second source verified and the original info little understood. So take it for what its worth. And those better informed, please correct-I don't mind if its not personal.
C1 is a cultivar of tetraspis. All C1 should be clones from a tetraspis found in the wild near former speciosa habitat. (I have doubts that all such labeled are clones).
Until a couple/few years ago, speciosa was thought to be extinct. I don't know where the recent speciosas came from.
There is/are physical/structural differences noted in the original findings (I think Naoki mentions number of callus sets on his thread).
Tetraspis can flower white, white with red bars, white and red spots/petals/sepals or even all red. I think C1 is suppose to flower with white/red petals and sepals.
There were long discussions a few years ago but don't know where it stands now.
Here is
Bernard Lagrelle's take on speciosa and on
tetraspis.
You'll have to pay me to do more research. I just want to enjoy the pretty flowers.