Unsigned and Brown?
Berry was a prolific correspondent, and we're fortunate that she was an exceptionally fastidious record-keeper as well. She and her office staff retained copies of nearly every letter she and the Schools sent.
This correspondence is recognizable by the distinctive slow fire effect which has degraded the paper quality (i.e. by the evident embrittlement of the paper resulting from acid decay).
Because these documents are copies, in most instances they are unsigned. But we are confident nonetheless about their authenticity and about Martha Berry's role as author. When you're editing, if you encounter an 'unsigned and brown' (like the one below) you should ascribe authorship to Martha Berry.