That is a shame.
My inner tinkerdwagon is already mixing up the epoxy, and shopping for some 800-grit emery film & black epoxy paint.
mnem
maybe CA would be a better choice with this Bakelite... and epoxy as filler...
Epoxy with finely ground Bakelite or pure?
My process with repairing this sort of damage is to collect every last sliver I can find, see how much can be jigsaw-puzzled back together, and from there decide whether assembling the parts dry and wicking CA into the crack or applying gel CA or epoxy then assembling, and in what order to assemble, is the better choice.
This pretty much depends on how the cracks occur and are willing to be pieced together vs much gap needs to be filled.
After that, I fill any voids with epoxy as filler, then the usual sand, prime, & paint with a high viscosity paint like epoxy or deck paint.
Very rarely, I get a break clean enough that it is less noticeable to dry-assemble the parts and wick CA in from the back side. With Bakelite, it is very hard to get a perfect paint finish due to how porous any break in the surface is; whether sanded or crack, any region that is not still shiny from original production soaks paint up like a sponge, requiring many layers of primer first to get a uniform finish.
In most cases, it is simplest to assume you'll have to do the whole "glue, fill, sand, prime, wet-sand, prime, paint" schtick than to hope for a quick simple fix.
Either that, or be willing to live with a visible repair, as I did with the crack in the back cover of my Simpson 635.
I looked, but I can't find any of my finished repair pics of that aside from the cracked-near-in-half leather strap.
mnem