I recently serviced this rare King Seiko Hi-Beat 4502-7000 vintage watch for a ClockSavant customer. This watch was introduced in 1969 and followed a trend of the era aimed at achieving higher accuracy by increasing frequency. With many watches running at 18000 beats per hour (bph), 21600 bph, or maybe 28800 bph, the calibre 4520 raised the bar to 36000. The Swiss were part of this trend also and had a number of calibres running at the same frequency such as the venerable Girard Perregaux Gyromatic. In servicing the 4520, several items were encountered. The mainspring broke at its weakest point, the rivet. The watch uses an unusually thick mainspring given the size of the calibre. As replacements are no longer available, a replacement had to be is identified based on calculations and the inner coil needed to be reshaped to fit the smaller Seiko barrel arbor, a task made considerably more difficult than usual due to the brittleness of the thick mainspring. Also Seiko shipped these watches with washers under the balance cock to address manufacturing variance in the fit of the cock to the mainplate. This is unusual and this particular watch had a balance cock that was replaced in the past and its endshake was not adequately addressed via these washers. The past watchmaker’s solution was to leave the balance cock screws loose which obviously was not a good idea. After being full my serviced and with these issues addressed, the watch is now running well again.
