English gold open faced one minute tourbillon lever Circa 1914

Gold keyless lever with one minute tourbillon by John Sutherland
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An extremely fine and rare English 18 carat gold open faced keyless lever pocket chronometer with one minute tourbillon regulator, circa 1914. Frosted gilt half plate movement, 20 jewels, pointed tooth lateral lever escapement with gold wheel, anibal-brass Guillaume balance, freesprung blued steel balance spring with outer terminal curve, one minute tourbillon regulator with polished steel three equidistant arm carriage drawn from that of Nicole Nielsen’s second type, polished steel skeleton single bridge. White enamel dial by Willis with Roman numerals, outer minute track, subsidiary seconds and original blued steel pear hands. Polished case by Frederick Thoms, master mark FT, swivel anti theft pendant, five bar hinge, glazed gold rimmed cover to view the movement. Movement signed, dial numbered, case with London Hallmarks for 1904. Accompanied by the original Certificate.
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Diameter: 55 mm
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Signed: John Sutherland 38 Cranmer Road Forest Gate London
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Awarded a Class A Certificate by the National Physical Laboratory, Teddington, Middlesex, accredited as ‘Especially Good’ in 1914, with a total of 86.9 marks, passing with superior merit.
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Extract from the results of the rating trial from March 2 to April 15 1914: 
The mean daily rate, in pendant up position: – 1.1″;
the mean daily rate, in right position: – 0.6″;
the mean daily rate, in left position: – 0.1 “; 
the mean daily rate, in dial up position: – 1.4″; 
the mean daily rate, in dial down position: – 0.7 “; 
mean variation of daily rate: +/ – 0.28 “; 
mean change of daily rate for I ” Faht.: +/ – 0.07 “; 
difference between the extreme: 5.2 “; 
number of the above marks awarded In respect of variation of daily rate: 34.3; 
in respect of change of position: 37.4;
in respect of temperature compensation: 15.2;
total: 86.9
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This watch was prepared and then submitted to the N.P.L. by John Francis Cole of Usher & Cole, presumably on behalf of the owner, some ten years after it was made. Cole was an outstanding springer and timer and would have been personally very familiar to the staff. His father, Richard Wright Cole, died in 1919, Joseph Usher having done so in 1903. None of J.F. Cole’s sons joined the firm but they continued running Usher & Cole Ltd. until he sold it to Camerer Cuss on his retirement in 1955.