Buyers should require the seller to respond to all reasonable requests to verify they have the item and will perform a sale as expected.
Make every effort to prove the seller has the watch. If the seller can't produce a photo of the watch with the date and a spoon or potato or today's newspaper or whatever you choose, then you're probably being scammed.
PayPal Friends and Family has no recourse. Sellers can consider Goods and Services and ask the buyer to be verified as well. PayPal friends and family with a $5 fee means it is an international payment.
A suspicious, unverified seller requiring Friends & Family (or any other means where you will not have recourse) means you're probably being scammed.
If you feel like a deal is so good that you need to act fast before someone else gets that deal, you're probably being scammed.
If the seller has zero transactions, or no history here, or zero transactions/activities in any other channels or subreddits, you're probably being scammed.
If the seller refuses to be verified, or refuses to post a tinestam photo with the sale item, you're probably being scammed.
If you communicate via chat, you should know that chat history can be deleted! If you are communicating via chat be sure to take screenshots.
If you have posted an item for sale, please be sure to include a username and timestamped photo with the item.
Don't be stupid and get scammed.
Be smart and get a watch.