Here's the breakdown for your serial number 5WA12-3854...
5 = Kansas City, MO Assembly Plant WA = 1940 1-1/2 ton 133" wheelbase 12 = Month (December 1943) 3854 = unit number starting with 1001. So, you have the 2,854th WA out of plant 5.
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD