A little history lesson before we get into the amount of grill slots....
The WWII Willys MB had a 9 slot grille that was initially designed by Ford for their GPW. The ford grill was lighter then the Willys designed steel slat 13 slotted grill. The Ford design was lighter and easier to manufacture. The grill on the post war jeeps were reduced to 7 to enable Willys to trademark the grill design because it was a significate enough of an amount of change from the trademark.
The 7 slot grill was kept up until American Motors came out with the 10 slot grill in '84. No significant reason, AMC just wanted to put their own spin on the norm, much like with most of their products.
The grill is the most identifiable and attempted copy piece on the Jeeps. As gm is pointing out, a lot of history in the grill including law suites on manufacturers trying to copy it. Take a pic of that grill and post it for gmwillys to look at.
Hey guys - this isn't all that big a mystery. Trucks are different
Look at the two grills; the '48 truck and the '50 wagon both have the same 10 slot grill. The tell tale is the flat front - no nose and flat fenders. There have been some holes added or enlarged for the extra lights and something behind the grill- but it looks like the trucks before they made the change to the F-134, the clock instrument panel and the peaked fenders.
The circle/4 hood emblem is new to us - but none of us are surprised about maybe a '49 showing up as a '50 (titles and bills of sale were changed by Willys-Overland back then). 1950 was a transition year - the "new" style was sometimes called the "1950 1/2".
I'd call it an early 1950 or maybe even a '49.
Is there an original serial plate we could check?
Later entry: The metal work joining the fender to the grill is a bit different on the wagon - fender is just one piece on the wagon, added piece on the '48. Same six bolt bumper though.