Gilbert was not the first American company to offer 3/16" 'S' scale trains. The Cleveland (Ohio) Model & Supply Company had been offering theirs (known as "C-D") by '37. But the smaller scale (1:64) became much more prominent with its introduction in the 1939 catalog, which features World's Fair imagery on the yellow, black & white cover. The relatively expensive, heavy and highly detailed engines and cars had had diecast zinc alloy bodies. As were the HO rolling stock, the engines and cars were offered in completely manufactured and kit forms. Additional engines, cars and accessories were added in the 1940 catalog. These included less costly engines with tinplate tenders, and less costly freight and passenger cars, also made of painted tinplated steel. The 3/16 scale trains were designed to run on O gauge track whose curved sections had 20" radii (formed 40" circles). Importantly, the trains featured fully automatic coupling and uncoupling that were functionally comparable to Lionel's. Unlike Lionel's costly and sophisticated design (each truck contained a solenoid and electrical pickup shoe), the A.F. 'link & pin' (a.k.a. 'harpoon') couplers were gravity based.