This seems to have been a common occurance with Sellier and Bellot ammunition, at least for pistol. I have instances of this in 9 x 18 mm Makarov cases. Some I found in ammunition I shot; a couple were sent to me by a friend in Republic of South Africa. It cannot be excused by any explanation, in my opinion, other than poor quality control at the time this stuff was made. We don’t see it here anymore, since all of the S&B ammunition we see now, other than old stock laying around, is Boxer primed.
The ones I have seen have had one, two (normal, except for poor positioning of the holes), or three flash holes. I have not seen any with such a huge number as six. It is hard to imagine how this could occur in production; harder yet to imagine how it got by inspection!
I believe I have alluded to this problem on the Forum before. Not important. A photo is worth a hundred words. Thanks for posting these good pictures Vlim.