Many American military secrets that are not available to China, can be obtained via shipments of scrap. For example, in 2003, an American company (State Metal Industries Inc., of New Jersey), signed a deal to dispose of surplus components of U.S. Sparrow (AIM-7F) radar guided air-to-air missiles. The Sparrow components were supposed to be melted down, and not, under any circumstances, shipped out of the country intact. However, the company made a deal with a Chinese firm to ship the missile components (the guidance and control system) in a shipping container. The missile components were hidden under a lot of other scrap, at the back of the container. But U.S. Customs inspectors discovered the parts and prosecuted the firm.
While the F version of the Sparrow entered service in 1976, it was the basis for many other similar missiles, including the current Sparrow version (AIM-7M), that entered service in 1982. Indeed, the 7M version is considered just an improved version of the 7F. The Sparrow has since been replaced in American service by the AMRAAM, but remains in use by many other nations. While in some respects a museum piece, the Sparrow was one of the first air-to-air missiles with all transistor guidance and control systems. It was also a very effective design. Chinese engineers could have learned much from it. Actually, the Chinese probably already have the components. Some 5,400 of the 7F model were build, and even more of its successor, the 7M. Most of the 7Fs, and many of the 7Ms have been scrapped. China knows who does the scrapping, and has people ready to make a deal.