Lorch LAS saddle stop

Firstly, I apologize for my lack of language skills. Australia is my single language

I have seen a few LAS posts on this site, so I am trying here first

I recently bought Lorch LAS that is missing a few parts. As shown in the photo1, it is missing the assembly to open / close the bronze half nuts. What am I having trouble with, where is the spring mechanism that opens the half nuts? I can not see where it would go on the side of the saddle that has the half nuts. It must go on the front behind the hub and lever?

Is anyone able to fill in the details of this?

Thanks, Jon

simon74 - thank you. I posted an email to Dr. David Lucy, but it was an automatic reply that he was on sick leave. The pin in the photo passes all the way through the apron casting and does not move. I think it could be a rotation limiter, or could be for a spiral spring type.

Looking closely at the apron, there is a 2mm hole where I am sure a spring located. On the opposite side of the lever shaft is a fixed pin that probably limited the rotation angle.

The spring type would then be a straight offset torsion spring.

Successful prototype