The first VIN assigned would have been 100001 as a general rule, but they were not made in order by VIN.

As one example, the first car built on assembly line 1 at Hamtramck for the 1970 model year had a VIN ending in 100052.

Its broadcast sheet sequence number is 1000001. (First Job) for assembly line 1.

If any car has a VIN with starting with a 0, my best guess is that it was one of the pre-production cars assembled by hand - not in one of the assembly plants.