I'm pretty sure each plant started with 100001. You could have two cars with the same VIN except for the plant code which would be different.

Your car is the 101019th car assigned a VIN. The other 101018 would be a mixture of car models. Even Dodge's would be thrown into the mix as well. Your car is the only one with a 201019 sequence # from that year at that factory. There wouldn't have been a Plymouth and a Dodge with that # at that factory.