Since this spring is not connected to the module, it has absolutely no electrical functions.
As you mentioned in post #8, for those springs to do a good job of shock absorption, there should be AT LEAST two springs, if not four, and the springs should be strong enough to actually DO some shock absorbing.
As it is, these springs are practically microscopic-- they're the size of the internal alarm springs -- so they're not really big enough to absorb any sort of significant shock.
In another thread (that I can't find right now) I'm 99% sure another member proved that the springs fit into holes which sit "outside" the rear O-ring, and connect the front bezel to the backplate. Thus, if there's static electricity when someone takes off a jacket, it's not going to jump from the jacket to the bezel and then THROUGH the module, which might short it out.
If you take a look at
https://www.watchuseek.com/f43/how-change-ctl1616-rechargeable-battery-41076.html in the Articles and Tutorials section, there are several pictures of the inside of an MTG-900.
I borrowed one of the pictures from Jacobe, and added one of my own pictures of an MTG-M900 without the bezels:
![Watch Diving equipment Dive computer Auto part Watch accessory]()
I can't explain why the spring isn't visible in the first picture, since I didn't take that watch apart, but it certainly LOOKS like the holes I highlighted do in fact go all the way through the case!
I mentioned losing the spring out of my MTG-M900 in my "Custom MTG-M900" thread as well, and had an interesting time replacing it. The first replacement spring I ordered from Pacparts was apparently an alarm spring, and was far too short -- when I dropped it into the hole it vanished completely, so I had to guess and order another spring with a different part number -- that one DID fit into the hole with some of its length sticking out, and I THINK it's contacting the back of the bezel now. Looking at another MTG-M900 I took apart, it looks as if there should be a small, "L" shaped metal piece that fits into the front of that spring, which then should touch the bezel.
The 8900 has that spring too, inside the case. If you look at this spring closely, you'd notice it's not connected to anything. It is just mounted between the resin case and the bezel ring. There is no circuit, no earth and no flow of electricity.
Second point to think of - any electrical connection outside the case is an exposed surface, which just doesn't make sense. What about when the watch is wet? The spring is completely exposed and will short out - defeating the purpose of any electrical connections it's supposed to be handling.
Third point - what if the the spring or the ring were to be dislodged on impact? Had they served some purpose like ground/electrical connection, an impact would knock the connection out, rendering some functionality useless. G-shock modules are designed to remain functional as long as the case is intact, so the possibility of an externally mounted vulnerability is completely improbable.
I can't speak for the 8900, but on the MTG-(M)900 and GW-(M)500 series, there's a small space on the inside of the plastic bezel where the metal bezel can make a connection.
If the spring gets wet, it's going to make an even BETTER connection between the metal bezel and the caseback!
The metal and plastic bezels fit together like puzzle pieces, and once they snap together they ARE "hard-fixed." Casio even uses double-sided tape to hold them together, but once those pieces are force-fit together and then snapped onto the case, they might as well be a solid piece of metal OR plastic. They will still absorb SOME shock, but no more than a solid resin bezel from a GW-6900.
