Ford GT40-Mercury question

Hello

I was wondering why, on some GT40 I have seen in photograph, it was written "Mercury" instead of Ford on the lower body stripe, such as this one :

 

Thank you to anyone who can explain me... (to my knowledge, there has never been a GT40 in the Mercury range.

 

Source: http://cs.scaleautomag.com/SCACS/forums/thread/964671.aspx

Leslie Marr Tony Marsh Eugene Martin