Most folks don't know about the Willys / Kaiser patent plate behind the seat. When the buy a M series Willys and the dash serial tag is missing they just shop for a used tag and stick it on there and voila you have a jeep with two serials and a lot of confused folks. A few folks want to believe that THEIR Willys came from the factory that way. I find that hard to believe. It is easier to believe the Army inadvertantly switched them during a serial tag inventory or something.
At any rate I would go with the tag serial behind the seat. Keep in mind that Kaiser stamped the factory 5 digit model prefix in front of the 5 digit serial. So the last five digits and the military prefix MD-Axxxxx would be you correct serial.
45 MB, 51 M38, 60 CJ3B, 60 CJ5, 76 DJ5D, Bantam T3-C MVPA22099