Original 1966 Seiko M-77 automatic advertisement, alongside an interview with Dr. William H. Masters and Virginia E. Johnson.
 
The Masters and Johnson research team pioneered research into the nature of human sexual response and the diagnosis and treatment of sexual disorders and dysfunctions from 1957 until the 1990s. 
 
They jointly wrote two classic texts in the field, Human Sexual Response and Human Sexual Inadequacy, published in 1966 and 1970 respectively.  Both of these books were best-sellers and were translated into more than thirty languages.  Additionally, both were the focus of a Showtime television series called Masters of Sex based on the 2009 biography by author Thomas Maier.
 
Dimensions: 10.25 inches wide by 13.5 inches high