Noun
An offset printing method utilizing a gelatin-coated zinc plate hardened and sensitized to print type, line illustrations, and fine-screen halftones.
A print produced by this method.
Source: en.wiktionary.orgPedlow and Welzenbach 1992, pp. 59–62, 66. The CIA assigned the cryptonym "Aquatone" to the project, with the USAF using the name "Oilstone" for their support to the CIA. Source: Internet