Gillis had worked in American naval intelligence , and enjoyed using his training to demonstrate to his friends how to determine that the same person had used different typewriters by the similar weight of their strokes .
Gillis ' staff of three searched bookstores and examined private collections .
Gillis had worked in American naval intelligence , and enjoyed using Gillis ' training to demonstrate to his friends how to determine that the same person had used different typewriters by the similar weight of their strokes .
Gillis ' staff of three searched bookstores and examined private collections .