It would be great if an agency manager tag was applied to accounts that are made agency managers and removed when no longer agency managers. This tag would make it possible to see what type of account it is when viewing it on an individual basis.
If you go to a user's profile from your site manager panel (Volunteerism > Users, and then click on the user's name), you can view the Agencies tab. There you'll find an "Agencies Managed" table that shows any agencies that the user manages.
While we don't currently have a tag (and adding it would require an enhancement), I hope this workaround provides what you need for the time being.
Thanks for reaching the suggestion!