Numerical identification
Most Lionel products can be identified by a four-number identifier. This is generally printed on the right side of a railcar or locomotive or stamped on the bottom. Some of their products also had a suffix of one to three digits. Not all models with the same identifier are the same. The company would make minor modifications to some models without changing the identifier.
Couplers
Examining the train&'s couplers is another simple way to identify the vintage of a Lionel product. Prior to World War II, the couplers were very toy-like, hook shaped and had no resemblance to a full scale train. The cars were metal and had very colorful schematics. Post World War II trains more closely resembled full-size rolling stock in color and used two different types of couplers. The entry-level Scout series couplers do not open, are longer and resemble a capital "G." The more common couplers open and are compatible with modern O-scale cars.
Electric Couplers
Lionel produced two types of electrical coupler. In his book "Getting Started with Lionel Trains," author and Lionel expert Allan Miller identifies them concisely: "Post-war also saw the introduction of electric couplers. The early version, immediately post-war, was operated by two extra rails either side of the middle rail. Each truck is in contact with these rails using contact shoes, and when a switch is thrown the power operates a solenoid in the coupler. The later type involved an inductive coil in the middle of the third rail reacting with a corresponding coil in the truck to provide electricity to the coupling. This was better than the first version since there were no contact shoes to get snagged with switch points."
Reading
Recommended by Lionel to assist collectors in identifying their products, Greenberg&'s Pocket Price Guide covers Lionel production from 1901 to the present, including models produced by Lionel LLC, which bought out the original company. It features in-depth analysis of models from all three eras of production: pre-war (1901 to 1942), postwar (1945 to 1969), and "modern era" (1970 to present).
Fakes
Original Lionel trains in good condition can fetch up to $1,000 and, consequently, replicas and fakes abound. Unsuspecting collectors can be duped by unscrupulous dealers into buying the products of Louis Marx and Co. instead. Although, their products are largely interchangeable, Marx locomotives and cars are slightly smaller and have less detail than the Lionel model train sets. Marx identifiers also have different numerical coding than authentic Lionels.