Never pay down a deposit in a bank account until you have met the seller, seen signed a purchase agreement.
No serious private advertisers ask for a down payment before you meet.
Receiving an email with an in-scanned ID does not mean that you have identified the sender. You do this on the spot, when you sign a purchase agreement.
For sale: Libratone Lounge soundbar. Plugs into the socket. Sounds good. New, or rather in new condition. Everything is included, including wall mount. Everything is sealed. Opened only for testing, and used a couple of times. Belgrade, Zemun, 350 euros.
