I lost the instructions and I’ve spent hours trying to identify it on the internet with no luck. It’s 3 rings with a metal chain with one removable ring. I’m stumped.
I think the objective is to separate the small ring from the chain. Also, it seems the chain goes around the S-shaped part twice. This procedure removes one of those loops, so you'll want to repeat it after you are done:
- grab the bit of chain just above where it goes through the S-piece
- pull all available slack to that part of the chain, make a loop out of the chain, and feed it through the nearest ring in the S-piece
- loop the chain around the whole S-piece, and pull it back through the S-piece's ring
This should entirely separate the chain from the S-piece, allowing the small ring to fall off the chain.