http://forum.chronomag.cz/index.php?...-kalibr-30110/
After subjecting the calibre to comprehensive upgrading, it operates with significantly less friction and its balance swings through a larger arc. IWC insists on closer tolerances for endshake, meshing and truing in the flat than ETA permits. A lever is individually made for each movement. Nearly all critical components along the path from the escapement to the mainspring are removed from the movement and replaced with corresponding components from IWC's own manufacture. The escapement and balance are optimally fine-tuned and painstakingly adjusted.
IWC buys at ETA no complete movements. The movements are only bought in its components, never assembled. In addition, only the best possible version is purchased - the so-called Chronometer version. Some components of the original ETA calibre's are immediately eliminated and are never used by IWC. They are replaced by usually more expensive and better ones.
The main parts IWC replaces are:
A. the mainspring
B. the barrel
C. the escape wheel
D. the pallet fork
E. the complete balance including the balance spring
The entire escapement is a good example. It is ordered separately with different, more exact technical IWC specifications and is only fitted into the calibre at the end of the assembly.
(...) Base plate is perlagée and the upper plates decorated with côtes de Genève.