A portrait of an anonymous person identified as a physician by the ring on his left thumb. According to some scholars, the sitter may be Luis de Mercado, Felipe II's chamber doctor; or Rodrigo de la Fuente, a personal friend of El Greco and a very influential person in Toledo at that time.

This work is listed in the 1686 inventory of Madrid's Alcázar Palace, where it remained until the fire of 1734, when it was transferred to the Buen Retiro Palace, also in Madrid.

It is signed in lower-case greek letters over the book.