The Autobiography of F.B.I. Special Agent Dale Cooper (1991)

Scott Frost's 1991 tie-in novel to the television series Twin Peaks presents itself as transcripts of the tapes Dale Cooper has dictated since boyhood; Cooper returns in Twin Peaks (2017). The entry for his fourteenth birthday, in 1968, already shows the investigator's method. (Open Library)

Watches

Timex watch: Given a Timex by his parents for his fourteenth birthday, the young Dale Cooper submerges it in the bathtub for fifteen minutes and records that it still ticks. The maker is named; the model is not.

Source text: Turned fourteen today. Mom and Dad gave me a Timex watch. I submerged it in bathtub for fifteen minutes and it still ticks. (Scott Frost, The Autobiography of F.B.I. Special Agent Dale Cooper: My Life, My Tapes, scan cataloged as Pocket Books, 1991, p. 16; Internet Archive scan OCR)