Ok the number you provided seems to be a commission number from at a guess after 1981.
Possible as I had a 1982 pickup.
It could be that someone did not see the VIN plate when doing the paperwork or the VIN plate was missing but the Commission plate was still there.
As you may be aware commission numbers are not recorded as well as VIN numbers. Though BMH may have it on record but it would cost you to get the info.