There’s a new rumor circling online that FanthaTracks (Star Wars Underworld, Bleeding Cool, and Making Star Wars helped out as well) has uncovered the working title of Stars Wars: Episode IX. They say it’ll be working under the name Black Diamond, stemming from information connected to the faux production company Carbonado Industries.
Our friends over at JediNews reported (writer now at FanthaTracks) on Carbonado Industries name over a year ago, posting the information back in August 2016. They were under the impression it was connected to the Han Solo film due to Han being frozen in carbonite in Empire Strikes Back.
JediNews suggested that PLT Productions was going to be the production company name for the Episode IX offices at Pinewood.
In September, director Colin Trevorrow exited and likely took whatever production names with him. We’re thinking that if this Black Diamond title was attached to the film at one point it was from the Trevorrow incarnation of Episode IX or a very early version of Han Solo’s title before Red Cup was used.
Omega Underground‘s own information seems to refute the working title currently. A recent December listing for Episode IX has J.J. Abrams set as the director (posted below with production numbers and addresses removed). No mention of either Black Diamond or Carbonado Industries, if they’re actually using these names it would have appeared here.
However, PLT Productions is indeed listed. 
It’s possible that their information is a little outdated. Abrams also isn’t likely going to use someone else’s production title, he changed Force Awakens’ Foodles to Avco, so it wouldn’t be shocking if he’s using another informal title.
As we’ve previously reaffirmed, Episode IX begins shooting this June at Pinewood Studios UK.