As I learned, a 2526 WG with WG baton markers is extremely rare. The retailer's signature adds more proof of originality of the watch, while not necessarily making it rarer.
Thanks Suitbert for sharing the post here. I did miss it in the General forum.
...which series are more rare. However I know there are people who prefer the first two series because they were more difficult to make.
From the market price perspective, I don't see much difference among the four series (mostly for YG). Regardless of which series, the most critical thing is the condition of the dial if it's enamel, which is mostly the case for YG.
I'm not sure if it's appropriate to discuss the concrete price figures here. I'm sending you a PM about that.