This lot is accompanied by a certificate from The National Physical Laboratory, Kew Observatory, Richmond, Surrey issued to Stauffer, Son and Co., London stating that the watch had been submitted for trial from November 1st to December 15th 1911, in which it received an especially good class A certificate with 81.5 marks, and subsequently was presented for test in August 1913 and again in July 1914.
Reinhard Meis in his book Das Tourbillon, page 355, lists three Tourbillons supplied by Nicolet, Fils, Chaux-de-Fonds to Stauffer, Son & Co., London which were presented to Kew for testing. The case marked CN on this lot would seem to indicate that it originated from Nicolet, Fils, and, although unsigned by Stauffer, was destined for a specifically accurate use.