When we talk about the development of the No. 3, commercial vs. the Russian contract revolvers, American collectors look at it the wrong way. When the original Russian contract was signed, the changes were the improved cartridge, Cyrillic barrel stamp and the lanyard ring. Before production actually began, more changes were requested by the Russians. The initial Russian contract production has all of those requested changes. This does not include the enlarged trigger pin and new hinge pin which were requested after contract production began.
All of the Russian requested changes were incorporated into commercial production as old commercial parts were used up and the Russian production parts were available. That is why all the changes in commercial production were not incorporated at one time but gradually as the old early commercial parts were used up.
I will make a separate post with all of those changes and pictures showing the differences and information when the changes were made in commercial production.
As to the notch and the extra lanyard ring, I have no idea. I got these pictures day before yesterday and am trying to find out more about the revolver.
Joe