Which model 123 you you have?
There are two now. The newer one has a hole in the side
of the distributor body in which you inser a USB cable, link the distributor to a laptop, and then change the curves. There is no selector to turn. With this model you don't need to remove the distributor (as I understand things) since the hole in the side is accessible in situ.
The older model, which I have, has a hole in the bottom
of the distributor body - not in the shaft which you show in your photo
With this model you ARE going to have to remove the distributor from the car. It is impossible to remove the plug otherwise.
The hole is plugged with a threaded plug which uses an Allen wrench to remove it. The hole is not quite as big as your little finger but easy to notice. The plug is very long... And a pain to remove. If it is missing a rubber plug will do fine to replace it.
If you do have this model and just can't see the selector way, way down in the hole, you hopefully can detect the shape of the selector 'knob'. It has a "+" slot in it for a tiny Phillips driver, and one end of the "+" has an arrow shape like this ^ to indicate that leg of the "+" is the selector point. Yes, the identifiers ARE TINY
but if you can identify just one of them, you can figure out where you are and work from there. I like the suggestion above of a bright light, a phone camera, and the zooming the picture up on your laptop.
Here is a link to the website that shows the orientation of the 16 curve identifiers.
If you need the decoder for what curves the identifiers signify, let me know and I will scan it and post it for you.
Good luck and keep us posted!