Yale & Towne Manufacturing Co., Stamford, Connecticut, 1 movement, Model LS31 (the Yale Duplex Time and Combination Lock™) pair

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These photos show a Manganese Steel Safe Co. installation of the LS31 time lock. The last two photos show, first the time locks removed from the bronze enclosure exposing the four tumbler lock beneath and second the opposite side where the exterior combination dial's arbor square fit into the combination lock tumbler drive cam.

Unlike the Yale's model K31 ½ where each combination lock was in the custody of two redundant timers, here each has only one. Yale's instructions for the LS31 made clear that if a movement stops during winding, the user was to remove that time movement with some small mechanical talent. (Closing the safe with the malfunctioning movement left in would leave that lock permanently dogged, and with only a single movement to release the other combination lock the risk of a lockout was always too great.) The resulting interim mechanism had one time-locked combination and and another that was not time locked - not ideally secure, but a useful compromise until the modular movement could be replaced, hopefully the next business day.¹

A. Model LS31. c. 1907. (sometimes called a 'bathtub' time lock due to the shape of the brass case housing the combination lock) and marketed by Yale as the Yale Duplex Time and Combination Lock. This time lock was designed specifically for use in a bank chest designed by the Manganese Steel Safe Co. Each lock contained one Seth Thomas made 72 hour movement along with a four tumbler combination lock. The safe contained a pair of these so as to encompass two combination locks and two time locks. Unlike most time locks, with the exception of Consolidated, these operated directly on the combination lock rather than the safe's bolt work.  Curiously, this arrangement seems to violate the redundancy principal incorporated in all later made time locks where there are a minimum of two movements used. This prevents an unintentional lockout should one movement fail. In this design we have two independent combination locks, each controlled by only one time lock each. To open the safe both combination locks must be dialed in correctly, so if one time lock should fail preventing the combination lock from being used, there would be a lock out. This configuration had been abandoned very early on and was only used in the early production of time locks used in Hall Safes. Production runs for this lock ran from 1904 through 1915. Of a total of about 2000 of these locks made, about 300 of these locks are now known to survive; fewer than 100 in sequentially numbered pairs. Movement #32,393 case#541 and #32,394 case#542. Two movement version. Cannonball type safes were one of the most popular models made and many time lock companies made locks that could work in this type of safe such as Diebold, Banker's Dustproof, as well as Yale's Y-361 and Triple L . file 17