Company Mergers and Demergers
If 2 organisations (with standard patent assignee codes) merge, Derwent's standard policy is to continue to apply the standard patent assignee code for each organisation as long as patents filed under the names of the independent organisations continue to appear.
For example, following the merger of Sandoz (SANO) and Ciba (CIBA) to form Novartis, the SANO and CIBA codes continued to be applied to those patents filed under the names of Sandoz and Ciba. These codes may ultimately become dormant if ongoing filings are made under the Novartis name for which a new standard code 'NOVS' was created.
Note that Derwent does not automatically assign a new standard company code when two large companies merge or are involved in takeovers/demergers etc. Each case is assessed individually and the most appropriate action taken. So in the case of Novartis (merger) and Zeneca (demerger from ICI) new codes were created, but with Smithkline Beecham, Bristol-Myers Squibb and Glaxo Wellcome one existing code was retained and the other abandoned.
Patentee codes are not generally changed retrospectively as Derwent does not track the assignment of patent rights from one organisation to another.