original_query: What is the significance of Guevara's heirs selling a copy of The Haywain Triptych to Philip II of Spain?
query: What is the significance of Guevara's heirs selling a copy of The Haywain Triptych to Philip II of Spain in relation to the authorship of The Seven Deadly Sins?
answer: The sale reveals that Guevara considered the Haywain Triptych to be a Bosch original, despite it later being identified as a copy.  This casts doubt on Guevara's reliability as a source for judging the authenticity of other Bosch works, particularly The Seven Deadly Sins, which he also discussed.