Thanks for all the good comments, getting closer. Let me reply on a few, and fill in some of the gaps so far.
The meter seems to need only 30 microAmps for full scale deflection which means that the clockwise force from the coil and magnet are quite weak and thus the anticlockwise force will be equally weak, meaning a very weak spring.
According to manual it is even as low as 8.8microAmps
No, it is not missing. It is clearly visible in the photo of the front of the multimeter in the first post.
However, now that I have looked at that photo more carefully I realise that the zeroing screwdriver slot is displaced to the right of the centre of the meter. So my mention of 6 o'clock position on the forked arm was incorrect. Can the spigot on the adjustment screw not engage in the fork slot when the forked arm is in the position which moves the pointer to zero on the scale?
Correct, that is the issue now, it seems I was not clear earlier. I do indeed have the adjustment screw (see new image 11 showing backside tap on screw). However, I took it out to show how it will not fit correctly in the adjustment slot once the adjustment lever is a position where the meter is zeroing. This is my main issue at this point (in first post, I could not zero it, but that is at least possible now, but will not allow using screw). I've updated image 4a showing the adjustment lever outline and the travel of the adjustment screw.
Okay, i see it in the first phot, my mistake. You have to "lock" the pin of the adjustment screw into the fork, then you can zero your instrument. So you have to change the position of the fork slightly to rotate the screw until it fits.
Thanks Frank, unfortunately screw will not fit the fork once latter is set to zero meter, see above.
In this case there appears to be a wire going vertically downwards from a solder joint that rotates with the forked arm. Possibly that is a spring which is operating in torsion mode.
Good with a confirmation, that is how I interpreted it as well based on looking at needle and wire while turning zeroing arm. Only heard of spirals before, never worked with analog meters inside.
Try moving the meter into various orientation and see if the needle 'zero' point remains reasonably constant. This will indicate whether anything has been bent in transit and upset the balance of the movement.
It does not. With the original "zero" at 5 on 100 scale lying flat on table, putting it on one side would move needle to 0 and putting it on the opposite side move needle to 10. Not sure if that is enough for it to be out of balance from transit, or it is just very delicate/accurate. It is made for use only lying flat.
Can you rotate the brown forked piece to have its slot at the 6 o'clock 3 o'clock (see my next post below) position while holding the metal piece with that solder joint to remain in the position shown in the photo?
This is exactly what I already tried: gently holding back either the left "ear" or the top part that wire is solder on to with a nail while turning. See updated image 3a with arrows. Nothing moved, but I did it very gently to not break anything so might not have used enough force?
All movements have a means of adjusting the zero adjustment range. This is in the form of an adjuster on the bottom end of the suspension - either the bottom hairspring mounting, or in this case, the other suspension band support. This is also moveable (although it doesn't have the same long adjustment lever. The correct procedure is to set the top zero adjuster to mid position, and then rotate the bottom one to bring the pointer to approximate zero position.
The ease of adjusting the bottom adjuster depends on the construction of the meter. You will probably need a long needle (non magnetic), or may even need to remove the scale plate to get access. One of the movement connecting wires will be soldered to this bottom adjuster - the wire getting accidentally tugged can be one reason for the problem occuring.
There is in fact a screw on the backside of the meter scale, inside the multimeter - see new images 9 and 10. It is made for adjustment, as there is a hole in the pcb to reach it. It has been fixed in position with (white) lacquer. Looking at the screw there is a something going through it, it might very well be an anchor for fixing the torsion spring. I did not touch this screw at I did not know what it was for. If indeed used to set zero range for the front zero adjustment, should I try turning this screw, or instead apply more force on the front adjustment lever while holding back the metal parts, to overcome the friction hold?