I have this course movement and upon disassembly, the mainspring literally fell apart in my hands. I sourced a mainspring replacement that I thought was correct (ETA 6497-1) only to discover that the arbor is much too small for this mainspring. Did I order the wrong mainspring or did OFrei ship the wrong mainspring? Their part : MS-65R, 6X5X18 1/2.
Thanks,
RMD