Having a devil of a time finding a mainspring for this watch. Have called Timesavers, Esslinger, McCaws, Daves watches Cas-ker, Cousins in Great Britain, no luck. It measures in Dennison 7x7x12 1/2 inches long, in millimeters it's Width 1.63x thickness 0.19x length 318mm the watch is a Tavannes 13 ligne movement an old trench watch. Serial number 39959. If anyone knows who else I might try would appreciate a response, thanks.
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