Much of the Bok material included in the portfolios and books published and authored by Petaja came from Petaja's personal collection. Petaja owned at least a dozen paintings, as well as dozens of sketches, drawings, prints and three-dimensional objects. Among Petaja's most beloved possessions was the first sketch Bok ever drew for him, a piece from 1936 called "Gleef," which hung on the wall of Petaja's San Francisco home. Petaja also collected examples of Bok's published work – such as magazine covers, interior illustrations, dust jackets, book covers, and more. Additionally, Petaja amassed Bok manuscripts (both published and unpublished fiction and poetry), as well as letters, books, other printed matter and unique, one-of-a-kind objects.