VIN numbers weren't used in America until 1954. Your plate# was the typical identifier of a vehicle in the 1920's. In the 20's car theft was only a widespread crime in LA and Detroit with fewer than 10% ever being found, identified and returned to the proper owner. Of the few car thieves that were actually caught a great number of them were or had been workers on vehicle production lines and therefore had the knowledge of how to "hot wire". LA had a plethora of cars due to Hollywood and wealthy ppl who could afford them. LA had he largest rate of vehicles to ppl of the entire country with one in two owning a car as opposed to the rest of the country where it averaged one car to every 6 ppl. It was much less likely you'd be caught in Detroit or LA as opposed to towns with much fewer cars.

There was certainly a market for stolen vehicles in the 1920's. one year around 11k were stolen in Detroit alone. Stripping for parts wasn't really a big reason as simply removing the plate would typically make the car anonymous. Unique features like customization was pretty much non-existent and with loads of the same models in limited colors on the roads made stolen cars almost impossible to properly identify. It's also thought that the notoriously corrupt Detroit police dept of the time (as well as LAPD) rather take bribes than make arrests since less than 50% of the 10% of caught car thieves were ever prosecuted. Unless they confessed the DA would have no real evidence that the vehicle in question was a stolen vehicle.

If the topic truly interests you there is a great book called The Automobile and American Life that covers the topic in-depth.

Follow up question: How would the police go about tracking down a vehicle in the 1920s?

Followup question; What was the process for being able to drive a car in the early years? Was there some sort of driving instruction/lisence for people that bought a car? Or was it just a chaotic free for all?

Follow up: if there was no customizing, how could people tell which car was theirs? Did they have to check their license plate each time? I've confused my car at the mall parking lot a couple of times, I'd imagine it would be hell with everyone having the same color/model

Follow-up: What was the penalty for car theft at that time? Were the penalties as steep as horse-theft?