[alexiskai]

I think it was pretty normal for parts to be evolved without iterating the part number. You see it in the service bulletins all the time, e.g., "The gas valve handle A-9191 has been changed from a forging to a stamping and the length of the shoulder on the gas valve reduced..." Both the old and new designs were filed as A-9191. Another classic example is the throttle control assembly. All variations of the assembly are A-9725.

I think they distinguished between part changes where the old and new parts are interchangeable except for some small detail (same part number) and those where the new part either doesn't fit the same as the old part or where the old part is deficient in some way where they want to expedite removal of that part from the supply chain.