

Timothy Treffry, Derek Pratt Watchmaker FBHI, British Horological Institute, 2012, p. 103
Derek Pratt hand finished the ébauche of the present lot at the Urban Jürgensen Sønner workshop in the mid 1980s.
N0 3001 is the second in the famous 3000 series of complicated pocket watches, which includes tourbillons, perpetual calendars and grand complications with minute repetition, split seconds and perpetual calendars. Each watch in the series is different and unique in its fabrication.
Although the series’ numbering reaches as high as 3065, according to the firm’s archives, approximately just 30 to 35 pieces were actually produced.
A testament to the complexity of the systems employed by Derek Pratt is the fact that the chapter ring for hours and calendar subsidiary dials were finished using five engraved plates for the separate calibrations.
The Perpetual calendar system employed in this watch is based on the system invented by Charles-Henry Audemars in 1862.