CYCLING (English newsprint magazine), December 18, 1963 reporting on the Milan Show mentions "one of the sensations of the show were the Cinelli interchangeable front and rear wheels." Shown in the photos is the 3-piece steel barrel and alloy flange version.
The article mentions the hubs being generally available (in England) by the middle of 1964. The first ad I have come across advertising the hub is a CYCLING Ron Kitching ad in 1965.
The article also mentions that they will be jointly imported by Ron Kitching, Hookstone Park, Hookston Chase, Harrogate, Yorks, and the Holdsworthy Col. Ltd., Lullington Road, London, S.E.20, and the price, including "block" is likely to be about £12 a pair in 36/36 drilling.
Chuck Schmidt
South Pasadena, California
http://www.velo-retro.com (NEW list of reprints and T-shirts)