For the first type, the textbook cites the Companions’ agreement on Abu Bakr’s caliphate (may Allah be pleased with him).
«كإجماعهم على خلافة أبي بكر رضي الله عنه»
Such as their consensus concerning the caliphate of Abu Bakr.
The usuli purpose of the example is to illustrate a recognized instance of openly expressed Companion agreement. Detailed historical reconstruction is a separate study.
The distinguishing feature for this category is explicit agreement, not merely the importance of the issue or the size of a majority.