I currently have a Heuer Siffert for sale on eBay and received a suspicious email (outside of eBay) offer to buy the watch. I played the game indicating a price much higher than expected on auction. I received the following email back, and I believe I've seen this ploy before:

Haussmann Watches & Jewelries
Calle del Príncipe de Vergara
22 28001 Madrid
Spain.

We accept the offer & if you have other available watches for sale
please indicate. We will like you to hand deliver to us in Madrid for
on the spot assessment and payment. Let us know when you plan to make
the trip so we make adequate arrangements for your pick up, we will
like to have it within the week as we have buyers on standby. Please
note that we will make refunds for your ticket to Madrid.

Regards,

John Klopper
Store Manager
+34631820633

Needless to say I've not bought my ticket to Madrid. Be careful!