is it the new or the old generation???

Unfortunately, the information on the site provided by your link does not include any model information. As you are probably already aware, there are five generations of the 802.11n AirPort Extreme Base Station (AEBSn). Since the link does state that the model being offered is "Wi-Fi con dual-band simultanea," it would be a simultaneous dual-band version ... which are the 3rd through the 5th generations.

I don't have the model numbers for AirPort specifically designed for use in Italy, but the following are the model & numbers for the US 3rd - 5th generation versions:

• 3rd Gen: Model# A1301 / Part# MB763LL/A
• 4th Gen: Model# A1354 / Part# MC340LL/A
• 5th Gen: Model# A1408 / Part# MD031LL/A

ho avuto lo stesso problema, ho acquistato ed ecco il risultato (verificato personalmente):

- MC340Z/A 4th generation;

- FD031Z/A 5th generation;

Mi domando se FC340Z/A (ora ricondizionata su Apple Store) costando meno sia della 4th generazione,
Quali sono i vantaggi della 5th rispetto alla 4?

Inoltre copio e incollo qui informazioni recuperate dalla rete:

Apple has had many generations of AirPort and AirPort Extreme hubs:

- AirPort Base Station 1G (1999), graphite: 802.11b WiFi, 1 10Base-T ethernet port, 56k v.90 modem, uses Lucent WaveLAN Silver PC Card

- AirPort Base Station 2G (2001), white: 802.11b WiFi, 2 ethernet ports (1 10Base-T for broadband modem, 1 10/100 for computer), 56k v.90 modem, supports AOL dial-up, uses 802.11B Apple AirPort Card

- AirPort Extreme Base Station 1G (2003, M8930): 802.11g, 2 10/100 ethernet ports, 56k v.90 modem (last model with modem), antenna port, USB port for shared printer

- AirPort Extreme Base Station 1G Mk 2 (M8799): eliminates modem and antenna port

- AirPort Extreme Base Station 2G (2004, M9397): adds power over ethernet (only model with this feature)

- AirPort Extreme Base Station 3G (2007, MA073, new case design): 802.11n draft, 3 ethernet ports, supports sharing a USB hard drive (AirPort Disk), eliminates power over ethernet

- AirPort Extreme Base Station 3G Mk 2 (2007, MB053): upgraded with gigabit ethernet

- AirPort Extreme Base Station 4G (2009, MB763): simultaneous dual-band 802.11n, adds support for a guest network with a separate name and password

- AirPort Extreme Base Station 4G Mk 2 (MC340): 802.11n final (no longer draft)

- AirPort Extreme Base Station 5G (2011, MD031): increased power and range for 802.11a, g, and n

http://support.apple.com/kb/HT4635