Hi!
For quite a long time, I am trying to get my Girard Perregaux/UG Moonphase with cal. 287 complete. It is similar to the one shown here: https://omegaforums.net/threads/girard-perregaux-gp-tri-compax-info.19737/#post-214232

Unfortunately, some parts are missing.
The first image shows the missing part.
The second image shows my watch where the part is missing.
Is anybody able to help with the missing part or knows how it is called correctly?
Thank you very much in advance!

Image 1: Missing part


Image 2: Movement of my watch