Regarding your question about the picture of Lord Caitanya with six arms...

Expressions researched:
"Regarding your question about the picture of Lord Caitanya with six arms"

1968 Correspondence

This form was shown to Ramananda Roy, and Sarvabhauma Bhattacarya. This is called Sadbhuja Murti.

Letter to Madhusudana -- Montreal 29 July, 1968:

Regarding your question about the picture of Lord Caitanya with six arms: This form was shown to Ramananda Roy, and Sarvabhauma Bhattacarya. This is called Sadbhuja Murti. This Sadbhuja Murti is worshiped also by the devotees of Lord Caitanya, and especially the Murti is situated in the temple of Jagannatha Puri. Sometimes when you may go to India and visit the temple of Jagannatha, you will find this Murti.