The rear press-fit splined nut does not remove for a clearer photo. Nothing I could ever capture in a photo, but you can tell the crack does seem go through the rear below the nut but tapers quickly to not travel all the way. Looking inside it cannot be seen extending past that press fit nut so it feathers out on the surface…
This comment showed up on velobase in 2014 by an “s barber” :
“These stems are sometimes found with a crack in the aluminum where the conical splines of the nut wedged into the alloy. These cracks are typically non-critical.”
There’s an unrelated comment above that by a wolfram verktyg… there is a user here named Verktyg also! Probably same?