What does the number look like? The military vehicles use NSN or national stock numbers that look like xxx-xx-xxx-xxxx (essentially a long part number), registration or US" numbers that looks like NLG420 or something of that nature, and serial numbers that are usually the oem serial number but could also be a coach builders s/n number if it went to another plant for chassis modifications. These are usually somewhere on a plate on the dash or glovebox lid for civillian type trucks. The few I have seen still had the regular vin number plate and stamps in the usual spots, but that doesnt mean that yours didn't get changed out, or had been removed.