A. Lange & Söhne

. . . On the left --- teeth profile of the stop works on ZW barrel, as shown on ALS website. On the right --- teeth profile on an actual model. As can be seen, the left pic shows a more defined and more angular teeth profile e.g. if you consider the centr...  

ALS has one version that "preloads" which is older and the other is a newer version with no preloading. I think the new one was updated in 2019. Ref #s are the same.

I looked at both older and newer movements which have the same teeth profile!

Have you tried reaching out to Lange for an explanation? Would be most interested to know the difference between the two.

not sure if it's less expensive and would like to hear informed opinion on that.

The stopwork system illustrated here is based on an orbital maltese cross. The outermost orbital cam with one less tooth revolves/pinwheels around the stationary central cam. They have a difference of one tooth, such that after a number of turns, the long...  

Thank you so much for the detailed explanation. I'll just add a couple of my observations, which differ a bit from yours, although I agree with the big picture about design optimization ... 1. I agree that the long tooth of the central wheel engages with ...  

I forgot about the balance wheel stop feature. In that case, it is entirely possible that the gear ratio of the barrel and second wheel between the old and new movements are identical, since the brake lever will stop the balance wheel before the barrel de... 

Thank you for enlightening us.

It seems the original movement had it as well. See, for example, Lange's stock photo and Peter's photo in his 2009 TZ article (both featuring lower tooth count on the stop works than the modern movement) below. In that case, it is likely that your origina...  

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