A seller's answer is a clue to what you can verify, not a verdict about their character. Pause when the details needed to identify the watch or document the sale remain unavailable.
1. “I can't give you the serial”
A seller may want to avoid posting the number publicly. They can still show it privately or at inspection. If they will not show it at all, you cannot check that exact watch against theft reports.
2. “The papers are for a different serial”
There may be a reason, such as a separate movement identifier, but ask for a written explanation and independent help. Don't decide that a mismatch is harmless because the seller says so.
3. “Pay now; inspect it later”
You need to know what is reserved, what happens if the watch differs from the listing, and whether the deposit is refundable. Get those terms in writing and identify the specific piece before transferring money.
4. “The old screenshot proves it's clear”
An old result may refer to another watch or an earlier date. Search the serial on the physical piece and save your own result.
None of these answers alone proves theft. Together, they can leave too many open questions. You can pause without accusing anyone.
Ask for What You Need to Verify
Get the serial, inspect the actual watch, and put the terms in writing before payment.