Concerning the seraphs in 6:2, see http://www.bibleodyssey.org/tools/ask-a-scholar/seraphs.aspx:
These seals picture basically the same scene portrayed by Isaiah in the opening verses Isa 6:1-7. The text on seal 273 states that it belonged to a courtier of King Ahaz named Ashna. In light of the similarity between the seal and Isaiah 6, it is worth noting that Jerusalem in the eighth-century B.C.E. was a very small town, that both Isaiah and Ashna lived during the reign of King Ahaz, and that Isaiah enjoyed very close connections to the royal court in which Ashna served (see Isa 7-9). Consequently, it is inconceivable that Isaiah and Ashna did not know each other.