Which textbook is this image on protein tertiary structure from?
The illustration is likely taken from a later edition of Baum's Introduction to organic and biological chemistry.
The first edition [1, p. 292] presents nearly identical illustration under a different number alongside with a note that the image was adapted from Bennett's Graphic Biochemistry [2]:



Unfortunately, at the moment (2020-10-16) [1] is available on The Internet Archive only for a limited amount of time for borrowing, and I was unable to find a full-text source for [2].
References

Stuart J. Baum. Introduction to Organic and Biological Chemistry, 1st ed.; Macmillan: London, 1970.
Bennett T. P. Graphic Biochemistry. The Chemistry of Biological Molecules; Macmillan, 1968; Vol. 1.