Compur Electronic 1 - missing spring?

I bought this as not working. It had signs of some heavy handed entry attempts, but otherwise is in pretty good shape. I opened it up and figured out the operation. It seems there is some sort of spring missing that takes the shutter through its open-close cycle.

Yellow arrow shows a pin with a groove that is most likely one of the anchor points for the spring, but I can't seem to figure out what king of spring that would be.

Has anyone worked on these shutters or just has a working one that they don't mind opening up an taking a picture of the mechanism? I can't seem to find any info on these.

Don't know, but Compur's mechanical shutters typically used a coiled spring such as this:

I found the diagram for this and other shutters here, but think it predates your specific model:
https://learncamerarepair.com/downloads/pdf/Compur-Factory-Shutter-Repair-Manual.pdf