Getting back to what happened to the OP, so.... he sold the watch at a forum collector price instead of trying to squeeze the last drop from the lemon. The buyer presented as a collector and the OP checked on him. A google search on the buyer last night came up with someone who matches who has a job; not 100% certain it's the same person but probable.
The OP told the buyer he'd be willing to buy back the watch if he ever wanted to sell it and the buyer agreed, not something a dealer would entertain. So, on face value he's not a dealer. Like 10's of millions of others, possibly the buyer's financial situation is affected by COVID business shutdowns and job losses and he needs to sell the watch. A way for both sides to come out of this positively is for him to sell it to the OP at a price that works for both sides, or they agree to sell it on C24 and share the profits. This way nobody is left bruised and reputations are preserved.