From the mailbag:

Mercury produced a line of pickups between 1946 and 1968. They were almost solely available in Canada. Many areas in Canada had a Ford/Monarch dealer or a Lincoln/Mercury/Meteor dealer, but few areas had both. In order for those Lincoln/Mercury dealers to sell trucks, Ford pickups carried the Mercury badge. Instead of the “F” designation, the Mercury line had an “M” designation. For the most part, the differences were cosmetic. If anything, the Mercury line was a bit more upscale, with a different grille or bumpers, often chromed compared to the plain Fords.

A 1957 Mercury Meteor Ranchero

The Automotive Trade Agreement signed between the United States and Canada in 1965 would bring about the end of the Mercury line of pickups. With the automotive manufacturers now being able to freely bring models across the border, the need for the separate line of Mercury M-Series ended, and the trucks were phased out by 1968.