it's a genuine nokia.
Majority work prefect, but will have minor differences too original brand new store bought n900's. there is a youtube video for a 'Fake nokia n900 unboxing' or.. something, it's not a fake nokia but it is a refurbished n900, i bought one also but i knew what it was etc.

The first tell is the box they come in, the embossed keyboard on the front has no spacebar. The box has cheap thin shiny black plastic inside, the user manual can sometimes be a photocopied book stapled together, you can see the corrugations in the cardboard when you open the box etc.. the phone itself, the plastic 'nokia' bezel surround on the front is black but the nokia logo is black not white, below the battery there sometimes might be a small oval sticker with a dragon on it, typically placed over the screw, from when it was put back together in china.

it's potluck with the 'made in Finland' stickered phones, some have new screens, some have new motherboards/keyboards etc etc.. all work fine bar one or two, it's just the accessories that come with them you need to be cautious for..eg.

the N900 i recently bought had a new screen, works great only setback is that it's a fraction dimmer than a genuine nokia screen. not a problem since the phone was only $160 aud.. However, the earbuds were random 'Noika' crap, the mini ovi suit CD had nothing on it and i went through 3 phone chargers since the first one i was sent overheated and literally blew up, told the seller( i was lucky i got a great seller) and he said he'd replace it with two new chargers and if they didn't work he would give me a full refund-one of them worked... but im using an old Samsung charger anyway since i don't want to start a fire in my house.

sometimes the battery's are knockoff's but sometimes you get genuine ones.

anyway, it's cheap enough and if it's a dud go though paypal and say you ordered a new phone but this is a refurbished one that's got X problems.

hop this clears everything up for anyone confused.