Since the arrival of the gen 3186, Rolex has changed the click spring. 657 is the original part and 657-2 is the 3rd gen click spring. They all will fit 3186, provided you have the right other parts.
If you are going to upgrade the ARF 3186, you need the following parts together to make it really reliable:
3186-260
3186-657-1
3186-665
Send it to misiekped . One of the most skilled watchmakers in this forum.