The Workbook is at 600 and the Text at 550, according to Truth vs. Falsehood. Here are the ranges, including the low-end:
Many students of ACIM believe this is true because it is referred to in the text by Helen Schucman but Doc mentioned the White Brotherhood were involved --request
From A Course in Miracles
ACIM teacher and his teachings.
Received "inner dictation" to produce the ACIM volumes. Calibrated as a spiritual teacher.
A Course in Miracles teacher
Spanish-language ACIM teacher, calibrated as a spiritual teacher.
ACIM-inspired writer and 2020 US presidential candidate calibrated as a spiritual teacher.
ACIM teacher calibrated