The second Mandala of the Rigveda has 43 hymns, mainly to Agni and Indra chiefly attributed to the Rishi gṛtsamada śaunohotra. It is one of the "family books" (mandalas 2-7), the oldest core of the Rigveda.
Witzel (1995) on the basis of internal evidence suggested that the second Mandala contains the oldest hymns of the Rigveda. In circumvedic tradition, rishi Grtsamada of Mandala 2 is a descendant of Sunahotra Bharadvaja (of Mandala 6), which would suggests a younger age of Mandala 2 than that of Mandala 6, favoured by Talageri (2000) as the earliest. There is no generally accepted relative sequence among the family books in terms of age: Being books preserved by individual families preceding the final redaction of the Rigveda into shakhas, they are all accepted to date to the earliest Vedic period, but considered themselves to be the parallel product of several generations.
Mandala 2 Wikipedia
The dedication as given by Griffith is in square brackets