1946 J. E. Hoover in Reader's Digest May 50/2 It was incredibly ingenious and effective, this micro-dot gadget. It perfectly counterfeited a typewritten or printed dot. The young Balkan agent, for example, had four telegraph blanks in his pocket, carrying Lilliputian spy orders that looked like periods; 11 micro-dots on the four papers.

1961 Daily Mail 8 Feb. 10/1 There was also a piece of glass with three microdots between the pieces of glass. These little dots are tiny pieces of film... By enlarging the dots again you can see what they contain. One microdot can contain a great deal of writing.

1968 Listener 1 Aug. 150/1 A house stacked with high-frequency transmitters, microdot readers.

1983 L. Deighton Berlin Game iii. 21 But that's all—no microdots, no one-time pads, no codes, no microtransmitters, no secret ink.

1999 Times 1 Apr. 43/7 When your husband tells you that he is a KGB spy, it explains a lot of weird stuff like having him jump out at you from the airing cupboard where he has been developing a microdot.

1971 Oxf. Times 10 Dec. 1/5 Produced 2½ microdot tablets in foil which were later found to contain LSD.

1972 Daily Colonist (Victoria, Brit. Columbia) 5 Jan. 1/1 Called a microdot, the deceptively small, purple pill packs super-concentrated doses of the hallucinatory drug LSD.

1989 R. Jones Transparent Gestures iv. 63 The little hits of psychopharmaceutical bliss the street kids still call purple microdots were delivered in plain Ziploc sandwich bags.

1999 S. Stewart Sharking vi. 96 In times of boredom, Dave had always been there, handing out microdots and leering at any girl present.

1957 Time 28 Oct. 22 Some messages were recorded on a film which could be softened and rolled into a ball; others were microdotted, i.e., whole pages of printing were reduced on film to pinhead size.

1969 D. Lambert Angels in Snow xix. 251 He decided to micro-dot the information and despatch it to Washington.

1974 P. K. Dick Pre-persons in We can remember it for you Wholesale (1994) 360 Then a copy would be on file. They microdot all those documents and records.

1961 Daily Tel. 22 Mar. 23/5 The wireless transmitter and equipment for micro~dotting at the house.

1963 J. Joesten They call it Intelligence i. vi. 61 Colonel Abel..did a brisk business in micro~dotting.