Holmes works out that Wilson has spent time in China because he's got a tattoo of a fish on his right wrist. And there's a smooth patch on his elbow, which is where he's been resting the elbow on the desk while writing. Holmes knows that that kind of pink ink is only available in China. Also, it has got a Chinese coin hanging from his watch chain. So all these things allow Holmes to understand what’s going on. He says: If I'm so candid, if I explain my methods so openly, then my reputation will suffer shipwreck. My reputation will be will be wrecked. Let's continue the story. Can you not find the advertisement,