I recently had this beautiful 6309 through and it received our new movement upgrade. The train wheel bridge previously had only 1 jewel and 2 bushes I have upgraded the plate to have two extra jewels which increase performance, amplitude, and timekeeping.
Below you can see the train bridge. The red on the bridge you can see is the existing jewel. The silver is the brass bushing. The brass bushings are hardened, but still much softer than synthetic ruby. The quality of hardness is what we are looking for from the ruby, as it helps to reduce friction, causing better results.
Here is a closeup of the bridge.
The bridge after the jewel upgrade.
Here is the watch assembled after servicing and upgrade.
Below we can see the results of the service We have a very respectable timekeeping result at +6 seconds per day and amplitude of near 260 degrees.
Seiko watches were designed to run at lower amplitude, but if we can increase it we will get better overall results. As you can see, the jewel upgrade is well worth the investment.