Looks like was typing this just as Jeff was typing his, but he beat me to the posting.
I agree:
MFG plates were (legally) moved from car to car, like a Dealer plate. The plate is "registered" to the manufacturer, not to any particular car.
Which is why you will see magazine tests (even today) with the same plate sequence on different cars.
The 013 is the manufacturer number. The little numbers on the left side of the plate are that particular plate's number.