You may have noticed a peculiar issue with many vintage watches of 1950s and earlier; the majority of them seem to have more ageing on the right-hand side than the left. I’ve spent more time than is probably healthy staring at dials and it has caused much head scratching and scrutiny as to why this happens. The explanation ‘that it’s the side closest to atmosphere via the crown‘ is a possible theory, but the answer to this perplexing question is actually rather simple:
During conventional wear, a well-to-do gent wearing a watch on his left wrist would undoubtedly be wearing a shirt with a sleeve. The position of the sleeve will inevitably obscure the left hand side of the face during a typical day. The simple explanation is that ultra-violet light that penetrates the exposed left side is what damages the delicate surface coating of the dial.
The result is what we call ‘spotting'; where the surface lacquer breaks down allowing ‘spots’ or corrosion to form in the metal surface below. Alternatively you might see a a more yellow appearance on this side of the dial as the lacquer deteriorates.
All this is very normal ageing and you should fully expect to see this type of ageing or ‘patina’ on a dial of 50 plus years vintage. Obviously for a valuable watch you should limit UV exposure as much as you can, but it takes many, many years of constant wear to show any visible problems, so it’s not something you should be overly concerned about.