The word "fiduciary", whenever used in this article, means a bank or trust company undertaking to act alone or jointly with others primarily for the benefit of another or others in all matters connected with its undertaking and includes personal representatives [including executors, administrators, administrators with the will annexed (cum testamento annexo), administrators in succession acting under a will (de bonis non), ancillary administrators acting under a will, and ancillary executors], special administrators, guardians, conservators, trustees, whether of express or implied trusts, custodians under the "Colorado Uniform Transfers to Minors Act" (notwithstanding anything in said act which may be interpreted as contrary to this grant of authority), assignees, receivers, managing agents, as defined in this section, and any other person acting in a similar capacity. "Managing agent" means a fiduciary acting in the fiduciary relationship assumed upon the creation of a relationship which confers investment discretion on the fiduciary, but as to which the technical legal relationship is that of agent and principal.