Does the pin open up all of the way across 180 degrees or does it stop a little bit before halfway at around 80 degrees? The reason I ask is that for many years now someone in the US has been making copies of N.S. Meyer flight wings using original dies. Original N.S. Meyer wings have a built in stop at the pivot point only allowing about an 80 degree opening while the copies do not and open all of the way to 180 degrees. From your photograph I don't see the squared off stop at the pivot point. I've attached some photographs of original WW2 era NS Meyer flight wings with the correct pin back stop that only opens up less than halfway.
Stop1.jpg
Stop2.jpg