The Nokia Lumia 800 and N9 were highly praised for their design, with one of the main characteristics being the seamless curved glass front screen.
This was expected in the Nokia Lumia 900 but we were told that Nokia was unable to do this as the integrity/strength of the screen was compromised or words to that effect. Evidently, having a curved large screen was solved as we will soon see this on the market again with the Nokia Lumia 920.
However, for those interested, above is what appears to be a prototype of the Nokia Lumia 900 but with a curved screen. I think it’s already a lot prettier than the flat 900. The screen appears to bulge out a lot more.
BTW, Nokia produces a lot of variants of their devices, different protos that as part of the usual design process does not make the cut. It could be as small as a curved screen or an old Windows button (as opposed to the new one) to something as great as a totally unreleased, unseen device on a totally different OS.