Good morning guys, I'm a proud owner of a black big eye with some unusual paint missing on the big eye, hoping you could help me make some new discovery on that!!!
Difficult to say for sure. However, since it's around the entire outer edge, and seems to be limited to damage to the Tachy scale, my guess would be that someone tried to "clean" at some point in time, and fortunately stopped before going further. Another possibility it that the watch had an oversized retention ring under the crystal, and if the crystal was moving, it wore away the Tachy scale printing. As for the Big Eye, the missing/faded details are likely due to a poor cleaning job. Either way, I'd say another dial would add the most value and best physical appearance to your watch.
If you are asking about the register on the right, I think that is the starting down count for a regatta event. If it the outer tachymatre markings, I think this is due to moisture and contamination and someone has tries to clean it unsuccessful.
Is it possible the dial wasn't correctly painted to begin with at the time of manufacture? It seems really strange that the 15 appears to be undisturbed given the red line would have bisected the 1 and 5.
I think an error from the manufactory is quite possible but not certain regarding the red line between the 1 & 5 I can't really sayd its look like was there but someone scratched off for some reason !!!