BOOKREVIEW What exactly do the Historic Mainspring Gauges for Pocketwatches measure? Mainspring Gauges and the Dennison Combined Gauge, by Richard Watkins. Published 2008 by the author, Tasmania, Australia; published as a downloadable and printable PDF file;, 50 pages, 28x21 cm, No ISBN number. 16 figures, 15 tales, 27 graphs; text in English. Available for free download at the author’s website http://www.watkinsr.id.au/ . Regular readers of the NAWCC Bulletin are probably familiar with Richard Watkins, the Australian pocket watch enthusiast, for his series of recent articles on ‘Practical Watch Collecting for the Beginner”, but may not know that he is a prolific producer of other horological publications. He deserves credit for publishing (mostly as free web-downloads) his English language translations of French horological classics, as well as a comprehensive Bibliography of the Mechanical Watch. His never-ending quest for horological knowledge and insights has recently led him to investigate the tools which pocket watch repair people for over a hundred years had used to determine what replacement mainspring to order. These pocket sized gauges are designed to roughly measure the height and thickness of a spring and in some cases the size of a spring barrel. Watkins is a most thorough researcher, who knows the horological literature well, but found only the most skimpy information on the subject in old or current publications. So he started to thoroughly investigate about a dozen gauges in his own collection and in the possession of some friends. These were made in France, Switzerland, Britain and the USA. The results are now available in the small monograph under review. In summary he found that: • The gauges by different makers use different and incompatible units of measure • The gauges provide a “Number” for mainspring height and a “Number” for mainspring thickness, but not a ‘dimension’ (e.g. a “Number 8 “ for height does not translate in twice the height for a “Number 4”). • Numeric analysis showed that most of the gauges, even those from continental Europe in the early 20th century, are based on subdivions of an ‘inch’ rather than metric; some gauges are based on British inches, some on French, and none indicate what they are based on. • Many of the gauges contain inconsitencies in their design and their construction. • All of them are highly inaccurate measuring tools. The new paper by Watkins adds much needed insight into a hereto under documented corner of the study of horological tools, and the author is to be congratulated for tackling the subject in his usual thorough and thoughtful manner. Fortunat Mueller-Maerki. Sussex NJ January 25, 2008 .