[TJ]

For many years the DMV in California required you to notify them if you made an engine change and they would put a DMV number(DR number) on the motor. They then put that number on the registration/ownership certificate to match the motor. Vehicles were in fact registered by motor number for years in California. I realize that is contrary from what we all know about old Ford ID numbers, but that was how California did it. After WWII it was found that innumerable cars had engine changes (to keep them running during the war) and people did not notify DMV. It made it very difficult for law enforcement and insurance companies to recover stolen vehicles. Over time the DMV decided to use frame numbers and body tags to identify cars. By 1955 the VIN system was developed and almost all manufacturers were using the body tags. The early VIN tags were spot welded in the left door jamb, riveted in the door jamb, or riveted to the firewall in most vehicle makes. Over time the VIN numbers got refined to give more information such as body style, engine type, body color, upholstery type, etc. The manufacturers then started using special rosette rivets to attach the body tags. The next step was to standardize the location of the VIN tag in all automobiles. As you can see the ID number system evolved over time and it took awhile to standardize it from state to state and manufacturer to manufacturer. All these changes over the years came about due to pressure from law enforcement and the insurance industry.