I belive Nokias tolerances are the same for every factory. I doubt quality is an issue in the Chinese handsets compared to the ones made in Salo. I'd say the ones made in China are of better quality since you're more likely to lose your job if you make a mistake in china when compared to Finland where it's almost impossible to get fired --> people tend to be lazy. Quality control is in place to catch handsets that aren't within tolerances.

Most quality issues with Nokias handsets are of a design nature rather than of a construction issue.