2892-A2, the watchmakers in Schaffhausen, Switzerland, have gone to the trouble of so luxuriously rebuilding the base calibre that you could almost describe it as
a total revision. The most immediately notable feature of the modified calibre is the gold plating. 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. I also read that IWC made recommendations concerning the original 2892 design, which were incorporated in the 2892A2.
The response I just received from IWC:
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.
The only difference between the movement 37524 and the movement 30110 is, that the first one 37524 is gold plated and the second one 30110 is nickel plated.