The name of the winning team is engraved on the silver band around the base as soon as the final has finished, in order to be ready in time for the presentation ceremony. This means the engraver has just five minutes to perform a task which would take twenty under normal conditions, although time is saved by engraving the year on during the match, and sketching the presumed winner.
When does the engraving take place? 
as soon as the final has finished, in order to be ready in time for the presentation ceremony.