This Adobe Type 1 font provides a good approximation to the rendition of the “important” blackboard bold letters from the old msym10 font, viz., C, N, R, S and Z. (There is a school of thought that believes that msym10‘s blackboard bold “looked better” than that of msbm10, but msym10 is no longer available.)

See also msx2msa.

The author is Berthold K. P. Horn.