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Product Description
If your Sony WM-1 does not Fast Forward or Rewind, then most likely the Hook Spring part is broken. These are impossible to find as they are no longer manufactured.
Original Sony part was 3-564-854-00 Hook Spring
Fits Sony:
WM-1
TCS-310
TCS-300
Sony TCM-111, TCM-121, TCM-131 possibly others in this range yet to be confirmed