I recently sold my N900 on eBay, the phone was a refurb from Nokia because my original's charger port broke, it was completely new from the factory apart from my old shell on the back as far as I could tell.
Anyway it was sat in my room for two years just collecting dust as I jumped ship to android, I cracked it open last week, gave it a charge, tested it and stuck it on eBay.

The person I sold it to sent me a message saying the phone charges intermittently, maemo browser often freezes and he took it to a phone center and they say it was overclocked.

I have a feeling the bloke is trying to pull a fast one and swapping his broke one for my new one as when it left it was absolutely perfect (well, I don't know about maemo browser). Is there anyway to prove the phone is the one I sent?