Yes of course sorry if I caused confusion.
HSBC is vague on this subject
It is possible that you will have several accounts with different entities of HSBC. Some of these accounts may require you to have a secure key. This is because HSBC Expat takes the security of its internet customers very seriously. We are constantly evolving how we keep you protected and Secure Key is the latest of these innovations. In the face of increasingly sophisticated online threats, it gives valuable added protection."
However this looks as if a mobile digital Secure Key can be used for more than one account. Internet Banking Support: lost HSBC details | HSBC UK