2.1. You may love patina, but for a lot of people it is still damage/decay so unless it's a special case, a patinated dial will lower the value of a given watch. As this subject is very, eh, subjective and a case of what one finds attractive take these points as mere guidelines.
Patina should be even on a dial. No matter if it's light spotting or the orangey-brown film of tobacco smoke residue from a long period of exposure to that particular element, you do not want random blotches on the dial, but instead an even spread. If the dial damage in question is pronounced at 3 o’clock on the dial there’s a good chance that the cause of the damage is a leakage around the crown, letting in moisture to the case.
Two cases of heavy dial patina, probably from tobacco smoke exposure*. Note that the bottom one is next to a very similarly dialled Seamaster that's also patinated, in this case more light and mostly in the middle of the dial:
(yes, they both were the same light colour to begin with!)
As "patina" could just as well be called "damage", this raises another issue - how about the movement? If you find a heavily patinated watch to your liking, you
must inspect the movement. Chances are that whatever caused the damage on the dial side has affected the movement too. Funnily enough, the word “patina” is rarely used on damage below deck...
In the case of black dials, there are several ways for these to age. Have a look in the "
Vintage Black Dials Only!" thread, where I have found some of the following examples:
Black fading to grey:
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In both cases the black colour is slowly losing its lustre and turning slightly grey. The text changes too and will, typically end up like the "Seamaster" text on the upper model and be hard to read.
Just like this:
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A pretty common variety of patina on a black dial is the "gold speck" dial, or the "starry night", where a number of golden stars dot the dial:
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This is due to the way the dial is produced: a layer of black paint is added to the brass dial, letting the brass appear where there is text. Eventually, the paint starts to flake and the brass peeks through. Simple.
Probably the most widely liked type of patination of a dial are of the "chocolate" or "tropical" variety. It is my understanding that to begin with, the "tropic" moniker would only be used on a black dial turned lighter brown, but now I seem to see it all over the place. Oh well. As mentioned, patina is a subjective thing and you'll have to make up your own mind whether or not you like it, and if you like it enough to pay a premium over a ordinary specimen. Most brown dials are due to paint defects and the effect of UV and/or moisture ingress.
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Quite a few blue dials - often those with a metallic finish - have also been known to change appearances. Here's a member's Omega Seamaster 176.007, which was a striking electric blue when it was new:
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The reason why I've focussed so much on black dials is that when these 50's and 60's watches were new, black dials weren't in vogue for a number of reasons. Black dial Constellations, apparently, were even a special order item. This means that there are many fewer of them - and due to the popularity of today, redialers will often paint their creations black! So if you are assessing a piece online and the black dial looks too good to be true (most have deterioated to some extent), then it most likely is. Tread very carefully.
*EDIT: I have now, some time after writing this post, come to the conclusion that correlating this particular type of dial aging with tobacco smoke ingress is probably false. It seems to be more likely to be a manufacturing defect in the lacquer, seeing that it often occurs in the same references and isn't spread evenly across several different refs.
