D&C 90

By revelation, the Lord said of the First Presidency -

"...verily I say unto thy brethren, Sidney Rigdon and Frederick G. Williams, their sins are forgiven them also, and they are accounted as equal with thee in holding the keys of this last kingdom..." (Doctrine and Covenants | Section 90:6)

Some may have intepreted this to mean that these two counselors also held priesthood keys or "oracles of God". But the Lord made clear -

"...through you shall the oracles be given to another, yea, even unto the church." (Doctrine and Covenants | Section 90:4)

In my mind, "even unto the Church" suggests the Quorum of the Twelve Apostles and then delegated with limiting authority to the Church. Even though it may seem so, the counselors in the First Presidency or any presidency doesn't hold keys. But as a presidency that is in unity, the presidency holds keys for we read of the bishop and his counselors -

"The bishopric is the presidency of this priesthood, and holds the keys or authority of the same." (Doctrine and Covenants | Section 107:15)

A simple analogy is that I am the licensing or qualifying person within my organization that is licensed in the state. As a result, I allow my license or authority license my business. Therefore my business has a contractor's license. Those autorized working under the umbrella of my business have authority to contract. If I was to leave, the contactors license of the business would be taken away until another qualifying licensed individual was hired by the company.

I see a the presidency to be the same where the president is the only one that holds keys. The counselors are equal in authority as a presidency.