A question for all you Zenith experts.

In my search for an A386, I have noticed many have what appear to be noticeable wear markings toward the outside edge of the rotor. See photo below for a typical example A386 (source: Zenith | Vintage "El Primero" Tri Color Dial ref. A386, made... for Price on request for sale from a Trusted Seller on Chrono24)



It also appears on other references with this movement as shown below on this A385 (source: ZENITH EL PRIMERO A385 Vintage automatic chronograph swiss watch Cal. 3019 PHC BROWN DIAL *** COLLECTORS *** Zenith Vintage watches - Watches83):



Does anyone know why this is occurring or have any theories on why it seems so common on this caliber? Could it be residue instead of wear?

This is the first movement where I have noticed such widespread rotor markings, so just curious as I learn more about the 3019.

 

Could be rotor rub maybe? Ive seen something similar on some Universal Geneve Microtor movements

 

Normally I would bet this is a sure sign of a weak rotor ball bearing so that the oscillating weight is grind onto the back a picture of the inner sight of the back could give a clue about this or someone used the wrong sealing for the back resulting in not enough space for the rotor weight.
Writing that this could be something that was fixed in the past by an watchmaker you have to experience the watch in your own hands for proof and with your ears to.

You can see that signs on any automatic rotor weight its not exclusive to this movement.

 

True but seems much more prevalent on the Zenith 3019. It is obviously a legendary movement, so I find the common rotor wear/markings very odd.

 

Kinda depends on how it was maintained, and by whom....... like used "pre-owned" cars.

 

Good point, Tex. Here are shots of mine, also looking clean:

 

I recently noticed a screw is missing maybe that is the reason for signs on the oscillating weight:



Anyway this movement needs service.

 

Missing parts and pieces are never a good thing, especially for a movement. That one appears to assist the pusher, and may not affect the freewheeling rotor.

Remember to find a WM that knows these movements, Zenith had to develop special lubricants for them.

 

Maybe the screw stuck between rotor and back.

 

Interesting points. Maybe these movements are prone to service-related issues because too few watchmakers are knowledgeable on their various intricacies (not that any watchmaker should ever miss a screw).

 

This movements are known as workhorses after a decent service they will run for another 20 years.

 

However, the second pic you posted of the A385 doesn't have that screw missing yet it has the same markings on the rotor. I'm wondering if it's just some kind of residue or grime build up that settles in that area, rather than caused by some type of friction.

The rotor on my A787's cal 3019 phc is clean, but I'm also curious as to what that is. I even see a little of it on the center edge of the rotors that @Gopher and @TexOmega posted.

 

Indeed, I do see that ever so faintly now on both. Might it be residue of the special Zenith lube that @TexOmega noted?