I do not remember where I saw this loop safety. It was quite a few years ago on one of the gun sites. I had the round stock to make the ring and was procrastinating on doing it. Yesterday I finally grabbed the bull by the horns and did it. The Mosin safety works like this. You load a round into the chamber, grab the back of the cocking piece and turn it to the left to put the safety on. The problem is that the cocking piece is a PITA to grab and turn because the spring has so much tension on it and the stock is in the way. With the ring, you just stick your finger in the loop, pull the cocking piece back and twist it an 1/8 turn to the left. It makes life easy if you are using one of these rifles for hunting.
Right now I am trying to purchase a quatity of cocking pieces to modify. I'm also looking into some stock for the rings. I will let you know shortly what happens.