Yes, happened to me fixing this broken Yashica FX3 that was a gift. Wound up with four of them in the end. They [FX3] used to be about $10 to $25 on e-bay a few years ago.
Where are you getting those part numbers?
What size and what vintage is the shutter? There were internal design changes made over the years.
The same size and vintage Compurs used in different makes of cameras have different internal parts although they all conform to the service manual layout and some of the parts will not interchange.
No, its just the index number of the diagram. Somewhere, once upon a time, there was a part number cross reference where the diagram number and index number had the part number and order information. Not needed for a discontinued device with no factory parts support.
The repair manual, https://www.scribd.com/doc/44503560/Compur-Shutter-Repair-Manual ,diagrams are called engineers diagrams and parts are numbered in assembly order.
An engineering tech would take the diagrams and box of parts and build the item for testing. Factory trained service techs would use the same diagrams to service the shutters.
OP -- We used to perform an occasional "TBR" -- Total Body Replacement -- in lieu of "repair" at the shop. Lift the bad body off the bottom cover (the part with a serial number) and slide the new working body into place....