I haven't swapped as yet, I have the same idea as you and will swap if/when the current chassis is really damaged.

As far as I can tell, its genuine. The only difference is the "Carl Ziess Tessar" font and most of the photo's I've seen online for comparison have the font from the new chassis. I'm guessing my Finland chassis is one of the original revisions. The buttons on the new chassis are actually perfect with no play at all and build quality is impressive. I cant say much more until I open up my current chassis and compare the insides but it is really well made.

The plastic wrapping is thin but its just there for no damage during installation. The chassis also came in two form fitting plastic bags, the outside one sealable. So the thin plastic is not really there for protection during shipping. These parts are not meant for the public and as such there's no "retail" packaging its just basic OEM type packaging.

Edit: Just found a good example of the font on the chrome strip from the new chassis its from an unboxing article for a white N9 here. So that makes me wonder... when did Nokia change the font on the chrome plate design and was my Finland chassis one of the first revisions? I prefer the font on my old chassis but I'll take no loose buttons over a font design any day