(a) When used with respect to an independent trust company, the head office or any branch office of such independent trust company.

(b) When used with respect to a commercial bank with trust department, the headquarters of the trust department of such commercial bank or any office (other than a place of business) of such commercial bank at which one or more officers or employees of such commercial bank are engaged on a substantially full-time basis in the business of administering fiduciary accounts.