Tick Talk[Moderator Emeritus]
2364
An interesting development!
Thank-you, your question has identified an error in my original post that will be corrected
Looking at the parts catalog, I find a reverser and reverser connecting wheel for the calibre 498/499 movement, so it is bi-directional winding. The JLC 493 they were based upon was also bi-directional. Very glad to have this set right...
On the matter of your automatic winding bridge marked P499, I can only speculate that it was the result of a later repair. While I cannot confirm the automatic bridges are identical (they were not offered in the parts catalog) your watch proves they are interchangeable.
After combing through my archives, I found one example of another 4870 with sub-seconds cal. 498. How close is the movement number to yours?