Magneto M-9F - UNUSED
Not refurbished, this one is N-E-W and still notches nicely. It includes a new rubber shear coupling that would be inserted below it in the accessory case.
The 'F' designation is for 'Fixed' timing - crisper engine response by design for aerobatic performance.
If you have run into M9-35 or -25 magnetos, these designate max spark advance degrees, also signifying that this is achieved by an internal mechanism, which takes time to respond. The benefit would be retarded timing in cruise with a few gallons per hour saved. Pop off the points cover and you'll see a rotor with one prong.
The Fixed Timing M9-F Magneto for sale here will have two prongs on the rotor since it requires the 'Shower of Sparks' system to get the engine started.
Only one thing worse than fitting the incorrect Magneto on your engine, might be mixing them up - one with fixed timing and one with auto-advance / retard. Have a look at the name plates on both your Magnetos next time you're under the cowling, to see they match. You won't be the first...Romanians had to use what was available to them.
You, however, have no excuse...