On March 27, 1930, the Horological School of Le Sentier registered specifications for a tourbillon regulator, which in time proved to be tremendously successful. Vacheron Constantin used this ebauche for their best tourbillons destined for Observatory trials.s.The design of this watch is very well thought-out: the arbor of the pallet fork is set outside the fourth wheel, allowing for a longer fork and facilitating manufacture. The entire carriage is very elegant, with symmetrically placed components; the escape wheel is symmetrical with the fork, the stud with the regulator base but placed on the opposite side for equilibrium. The poising bar placed on the opposite side of the escape wheel and fork bridge has threaded holes for poising screws similaro a compensation balance - also a very useful feature. The train from the third wheel is placed on a separate plate. The winding system, a combination of Adrien Philippe?s and LeCoultre?s rocking bar designs, creates a very stable system, eliminating the necessity for intermediate setting wheels and thus decreasing the resistance of the motion train which has a high number of teeth to ensure smooth transmission. The regulator has a provision for closing the pin?s gap, assuring a high level of ischronism.Many of these movements were kept by the company. Toward the end of the 1980?s Vacheron Constantin cased a few which were then sold to some of their best clients; this being one of them. Another, only two numbers apart, case No. 614923 was sold to Asprey, and chosen to represent the company?s achievements in the field of tourbillons in ?The World of Vacheron Constantin?, p. 231.