What do the titles C.S., C.S.B., and C.S.D. signify?

In a 1935 issue of the Christian Science Sentinel, the editor writes:

Frequent inquiries come to The Christian Science Board of Directors as to the meaning of the initials “C.S.,” used by Christian Science practitioners and Christian Science nurses in announcing their work. Some think they mean “Class Student.” Some think they mean “Christian Scientist” in the sense that one is a believer in Christian Science or an adherent of Christian Science. Actually, while their meaning is “Christian Scientist,” it is that in more of an educational sense: it means that the user has been under proper instruction in Christian Science, known as class instruction, and is entitled to the designation because of having satisfactorily completed the course.¹

The designation C.S.B. stands for “Bachelor of Christian Science,” according to a notice by Mary Baker Eddy in the February 1886 issue of The Christian Science Journal, and was originally used to designate a practitioner who had completed Primary class instruction.² However, there also was, during Eddy’s time, a designation of C.S.D., which stood for Doctor of Christian Science. This was generally given to students who had taken a class under Eddy and had continued as practitioners of Christian Science, in good standing, for three years. However, Eddy occasionally conferred the C.S.D. degree to individuals who had not taken instruction with her. (Adam Dickey is one well-known example.)

As this indicates, during the early decades of the Christian Science movement, the designations C.S.B. and C.S.D. were conferred on Christian Scientists who had not taken a Normal class and were not Christian Science teachers. In fact, for many years in the twentieth century, a precede to the listings of Christian Science practitioners in the Journal noted: “Not all who have the degree of C.S.B. or C.S.D. are authorized teachers,” and “The degree C.S.B…followed by (teacher) means one who has had Normal course instruction, and received a certificate.”

The designation C.S.D. was discontinued after Eddy’s passing, and C.S.B. is now used to designate teachers who have gone through Normal class, while C.S. is used to designate practitioners who have taken Primary class.