While I'm a bit pressed for time I will share some thoughts based on first hand experience repairing these movements. As my company has been the official service center for Porsche Design by Orfina since the 1970's I have serviced thousands of their models 7176/7177 which contain the Lemania 5100 movement.

I've read the discussions and many articles over the years and one reason collectors favor timepieces with this movement is the fact that it's perhaps the only chronograph that has a large central minute counter. Now, let's look at the movement from a watchmaking perspective. I think this movement was constructed with the express considerations of a simple, functional, and economical construction. It was never meant to capture the attention of a watchmaker for its aesthetics or for its ease of service.

The movement contains many plastic parts which give it a raw and cheap look though some will argue that plastic parts require no lubrication thus better performance. In my experience, the plastic parts in this movement present a whole different set of problems that can cause a headache for even professional watchmakers who are not experienced with this calibre. Quite often the large plastic support plate (#2737) on the dial side swells with age or from improper cleaning and, as a result, will jam the calendar date disc. Since most watchmakers are not fortunate to have a supply of parts on hand it can become frustrating to figure out which part(s) are defective and need to be replaced. Thus hours of wasted time and effort go by because the aforementioned problem is not visible to the eye.

The overall construction of the chrono mechanism is such that a set of levers and parts interlock and hold each other in place supported by the above mentioned plastic bridge covering the under dial side of the movement. This design also makes oiling a little tricky and different than the conventional construction of, for example, the Val. 7750. The train bridge side of the movement contain plastic bumper supports which act to buffer the oscillating weight agains sudden impacts. The small bridge (#1155), a.k.a. bar for reduction gear, is inexpensively made and more often than not the hole wears out rendering poor or no automatic winding. I never fully understood why the Lemania factory hadn't produced these parts with a hole jewel for longevity though the same argument can be made with the Val. 7750 small bridge (#8079) a.k.a. coupling clutch for oscilating pinion. Of course, as mentioned, this movement was constructed in the most economical way possible.

From a watchmaker's view there are other issues to reckon with. The amplitude on this calibre is rarely on the high side with the exception of new or slightly used excellent condition watches. Though it has a large balance wheel and a good shock system the staff pivots wear away slightly from use and very often cause a significant drop in amplitude. This phenomenon doesn't show up as often with the Val. 7750 chronograph movements. Yet, surprisingly, with proper and professional service I have seen the Lemania 5100 movements last over 30 years as they keep ticking away with decent timekeeping.

These are my thoughts without researching my collection of files.

Best regards,

Jack Freedman
SUPERIOR WATCH SERVICE INC