The grey-market with which I became familiar in the late '70's and early '80's was one in which some "surplus" dealers (meaning, in general, purchasers and resellers of "distress" merchandise which was over-purchased, or inventory of enterprises going out of business. Unfortunately, there was a small but well-known market for mismarked parts, usually commercial-grade parts relabeled (illegally) as military or space-qualified parts. On rare occasions these were actually dispatched into the military procurement stream, and, when discovered, caused quite a stir, and sending some individuals to prison.