I was looking for some watches on chrono24 so maybe I could share what I learnt so far...
1. Chrono24 is like a platform for anyone to advertise watches. To avoid scam, chrono24 would ask for the seller to post watch showing a specific time (like 3 o'clock).
2. Do some research on the seller on chrono24 before buying. However, you can see that not many would leave feedback...
3. Use reputable courier that provides tracking (FedEx). Sometimes you would need to pay for express but it's worth it
4. If the prices are way below market price, be careful and proceed with much concern
5. Insist on pictures of the warranty card (if not shown) before making any transaction