@foil_guy Here is a link to a post that indirectly addresses the issue above: https://omegaforums.net/threads/pretty-movements-anyone.35781/page-2#post-405812

 

thanks, in essence like a single pusher hanhart. As opposed to the chronostop that omega produced.

 

Yes. Longines also produced "chronostop" or stop-seconds movements: https://omegaforums.net/threads/tho...reviously-sold-at-hodinkee.68157/#post-855439

 

On a 13zn that is true. However, monopusher flyback do exist. I have one.

I believe there are at least two Longines Chronograph movements that can do this.

 

Is that different from a chronostop (i.e the chronograph continuously runs, and the button resets)?

 

Sorry if a slight tangent, here is a Ref 3795 next to the 13Zn Ref 3721. Interesting for size and style comparisons, of military format pilot watches of the era.. Another original but wabii'd dial. This one is an issued piece, with the F5357

 

Absolutely, 12.68Z and 18.72 chronostops. But, does not diminish DD12 main point that 13zn mono do not flyback.

 

I do not know the history of the words "monopusher" or "flyback", as they pertain to watch movements. But in my view, they are terms that denote an unconventional design when compared to the normal, two-pusher chronograph. Under this, admittedly, arbitrary assumption, it would not make sense to apply these terms to Longines' stop-seconds movements. I suspect that my motivation to operate under this assumption is that doing the contrary would undermine the functionality of movements like the 13.33Z, 13ZN, and 30CH.

 

I don't see a problem with calling them true Chronographs and a flyback. They have accumulation registers so it is possible to time a full leg. It resets and restarts a new leg instantly like a flyback is supposed to. Everything you can do with a 13zn flyback you can measure with a chronostop. From a timing standpoint, these were used by the US Navy for ship maneuvers. They were also used by the Scandinavian Navies. They are not gimmicks. The single button simplified operations and avoided button confusion.

Update: Some Flyback Chronostop pocket watches were ordered by the Bulgarian Royal Army.

 

In order to stop the chrono hands of a stop-second movement, constant pressure must be applied to the pusher. This means that one of the wearer's hands is occupied while the chrono is stopped. Furthermore, in order for the chrono to be stopped and not reset, a specific pressure must be applied to the pusher. This could be difficult to execute while wearing gloves, for example. Additionally, when the chrono has been stopped but not reset, the chrono second hand is prone to accidental movement due to the absence of a blocking lever or similar components.

The limitations outlined above are a consequence of the simplified design. And while stop-second movements are capable of being reset while running, they lack basic functionality that is indicative of traditional, flyback chronographs like the 13ZN or 30CH.

 

To summarize: They do operate differently and each has different advantages and compromises. For military use, the chronostop watch variations were chosen as well as standard chronographs implying that chronostop flyback movements met all functional requirements. A monopusher chronograph movement can be made to flyback.

 

If anyone isn't familiar, this is a flyback military Chronostop made for many Airforces, Canadian Royal Airforce, Japanese Imperial Army, Israeli Defense Force, etc. 12.68z flyback monopusher. View attachment 732462

 

Interesting 13zn. 34mm steel case with tapered bezel. It was completely authenticated with a right subdial misaligned. It is too high and too far to the right. This is a counter-sunk dial.

View attachment 733311

 

Another 34mm steel case tapered bezel and right sub-dial misaligned 13zn. The sub-dial looks too far to the right.

 

And only 3 movement serial numbers apart. Now with reinstated fixed bars.

 

Absolutely! Great catch Paul!

 

Well it's an ugly duckling Seiji , but I like quirky watches, so it fits in.

 

Original untampered 13zn steel monopusher...what's not to like?

 

It looks like a "military style" watch for sure! Monopusher 13zn don't come up often. Longines is often about rarity!