No case-movement match!
The extracts from the archives are based on the case books. The case books doesn't comprise the movement No., but only some details of calibre.
So:
If you send a movement No. only to Schaffhausen, you get nothing.
If you send a case No. only to Schaffhausen, you get an extract with only the calibre, but no movement No.
If you send case and movement No., you get an extract showing the case and the movement No. named by you provided the data on the movement match with the data on the movement noted in the case book. Otherwise you will be informed, that there is a mismatch and no extract will be issued. But in fact although "your" movement No. is given in the extract, nobody checked the movement No., but only the calibre.
Maybe by now it is possible for IWC to verify whether the movement bearing the serial XYZ left Schaffhausen in the case No. ABC. But in the past the records did not allow that (or only with unreasonable efforts).
So don't rely on the movement No. given, but on the calibre named only.
Hope this helps!
Th. Koenig
P.S. No details on the dial etc. are checked except these details are part of the Ref. No.