Hi
The term office manager is too general and in addition it also does not indicate the size of the office, the work profile of the individual or the KRA of the person.
In general any office manager must be a role model for the office in general and his team members in particular. So he/ she must be good in general management including time management, communication skills and leadership skills.
The specific functional skillset requirement would largely depend on the job profile to be handled. eg. if he is in charge of a branch office then he is a key link between branch and head office. In that capacity he /she must be competent with accounting, inventory and coordination. On the other hand if the person is an Office Manager in charge of the facilities of the Head Office, then the functional requirements would be dependent on the type of facilities he/she has to monitor.
Trust I have been able to give you an appropriate response.
Regards