Just reading the last few posts, Im not sure the following is in answer to what your asking. But Not all ink shut-off Dorics had screw in personal points. Some are friction fit. If this is so, there is no personal point collar to unscrew. Looking with magnification looking at the section from the front see if there really is a separation between section wall and the supposed personal point unit. Use some thin penetrating oil like pen potion #7 or the like and put a drop on the supposed separation. If the liquid recedes into the supposed crack between point and section youll know its a personal point. Is so, you need to unscrew it. Use gingers only. No pliers. If it does not budge use penetrant like Pen Potion #7 and 150 degrees heat. It will eventually come apart. However if ink has dried up over the years it can take a while to dissolve it to free things up. If its a friction fit, the unit pulls out. That said once the unit is removed youll see the spring is retained between to prongs at the ends of a cutout slot in the shut off shaft.
If my answer is not aligned with your question. Apologies.
Quite on point, Wahlnut! Many thanks.
Funny thing is, I have only JUST found out about Potion No.7 as I was looking for something like this, then I checked my forum activity, and lo and behold, your reply mentions the same.
I'm in the UK so not sure I have a potion No.7 provider here. Are there alternatives for us, UK-ians?
I'm pretty sure it's a screw-in personal point. I can see the last part of the thread when looking at the end of the section. No budging whatsoever. I've given it 4 rounds in an ultrasonic cleaner and water so far. Really taking baby steps here.
The pen is generally working, the burping itself has been solved by applying some silicone grease to the section-barrel threads, and I have managed to get the shut-off spring back in and fit everything well so that it works. But I still want to free up that personal point. I know I will need to at some point later when the shut-off-valve gasket eventually gives (not that I fly, but I would like this pen to be perfect. I overpaid for it after all just because I wanted it).