Same gun. Look at the label on the box. They made a VERY few Wingmaster Super Mags. All the rest are Expresses, and they all have the 3-1/2" chamber, and while the rollmarking varies its still the same gun on the inside. Some regular Magnums say Express and some don't as well.
Magnums, serial number ends in 'M' - unless they have added another letter, are chambered for 3". Super Mags are chambered 3-1/2" and the serial number did end in 'A', but I guess you can add 'F' to that one now.
Remington has been very fluid with their rollmarkings through the years.
What could have happened... did.