Curious case of 1/3 free slave

[Epictetus]

I would suggest that the original three owners were not very wealthy - otherwise they wouldn't have had to club together to buy a single slave. Perhaps they were neighbouring farmers with small plots, who bought the slave between them and shared his labour? Or co-owners of a workshop? One of them died or sold up and freed his 'portion' of the slave, leaving the other two (who perhaps still couldn't afford to buy the third 'portion'!) to share the two-thirds of remaining servitude?

In Westermann there is a long list of slave transactions (I was actually interested in the prices of things when I came across this). If we just look at the second century, it lists 30 different sales or notices of sales from across the Empire. Of the 30, 26 were transactions for entire slaves. Four were for partial shares: three for 2/3rds, and one for 1/5. So at only a 15% rate, it does seem that owning slaves in tandem with other shareholders was relatively rare.

It's a fascinating case anyway, but I expect rather a grass-roots thing, at the level of society where perhaps the boundaries between freedom and slavery were not as exact as we might consider them today...

Yes, this is exactly what I’m thinking, too. The modern mind might tend to believe slavery was a yes – no proposition: you were either a slave or you were free. But ancient Roman society seemed to be more complex. Freedmen were limited by legislation on their rights, and they had the social responsibility of being tied to the family who freed them. Even regular citizens had different levels of freedom and rights, depending upon if you were a honestiores or a humiliores. If it was possible for a slave to own 1/3 of himself, it seems that freedom was an extremely nuanced concept.

Edit:
PS

If I owned 2/3 of a slave, I'd allow him to be free for the 8 hours he slept.

Bravo!