What I can tell you is that this vintage postcard is part of a series of cards that City Chevrolet in San Diego sent out to potential customers. If you search around the net for "1906 Autocar Roadster" you'll find lots of car dealers used the same card, only the information on the back was different.
Click on images to see them larger.
I guess the big question for me is what company created this series and sold it to dealers? Where were they located and what else did they market that was used by a variety of companies?
UPDATE: Thanks to WJY I have some info about the manufacturer of this car:
Next time you see a garbage truck take a close look. You might see an Autocar logo. They're still in business. Your car was made in Ardmore, Pennsylvania.And this then led me to Wikipedia:
The Autocar Company is a Hagerstown, Indiana specialist manufacturer of cabover vocational trucks, mainly for refuse applications. Started in 1899 in Ardmore, Pennsylvania as a manufacturer of Brass Era automobiles, and from 1907, trucks. The last cars were produced in 1912, but the company continued as a truck maker until 1953 when they were taken over by the White Motor Company. White was taken over in turn by Volvo Trucks in 1980 with Autocar continuing as a division. In 2001, it was sold to Grand Vehicle Works Holdings, which continues to use the brand name for their line of trucks.
The company was called the Pittsburgh Motor Vehicle Company when started in Pittsburgh, Pennsylvania in 1897 but became the Autocar Company in 1899 when it moved to Ardmore, Pennsylvania, outside Philadelphia. One of the company's early cars was the Pittsburgher. By 1907, the company had decided to concentrate on commercial vehicles, and the Autocar brand is still in use for commercial trucks.
Based on the minutes of company board of directors meetings during 1903-1907 it is known that in 1903 the Board of Directors included the president, Louis S. Clarke, the secretary, John S. Clarke, as well as, James K. Clarke. Both Louis Semple Clarke and his brother John S. Clarke were members of the fabled South Fork Fishing and Hunting Club of Johnstown Flood fame.
Autocar founder Louis Semple Clarke (1867–1957) was a successful mechanical engineer. Among Clarke's innovations were the spark plug for gasoline engines, a perfected drive shaft system for automobiles, and the first design of a useful oil circulation system. Clarke's insistence of placing the driver on the left hand side of the vehicle led to that standardization throughout most of the automotive industry worldwide, and consequently we drive on the right side of the road. The patented porcelain-insulated spark plug process was sold to Champion and remains the industry standard.
Clarke was also a talented photographer. His family were members of the elite South Fork Fishing and Hunting Club above Johnstown, Pennsylvania, whose earthen dam at Lake Conemaugh burst on May 31, 1889, causing the Johnstown Flood.
Clarke sold his interest in Autocar in 1929 and retired from business. He died in Palm Beach, Florida, on January 6, 1957, and is buried in Allegheny Cemetery, in Pittsburgh. (SOURCE: Wikipedia)Click here to read about the various vehicles they built.