Finally, a Calibre 28 --the missing link to my pocket watch collection

After several years of searching, I've finally found and added a circa-1879 calibre 28 to my pocket watch collection. To me, it's the missing link.
The calibre 28 is a so-called Pfister movement, named after IWC's CEO of that era. It, and its companion Savonette calibre 29, are known as "a bascule Pilier" -French for "rocking pillar", a movement characteristic I don't fully understand. What is notable about the movement, aside from its relative rarity, is the full three-quarters plate.
I consider this watch as a missing link to my collection in several ways. It completes to my thinking my collection of all basic pre-1900 IWC calibres. The collection goes from Jones (3 different examples) to Seelands (2, including a rare Boston), now to the Cal. 28, and then to Elgins (a rare Elgin I and an Elgin II Pallweber) and then to several Calibre IWC's, early 1890s forerunners of Calibre 52s, IWC's basic pocket watch movement during the first part of the 20th century.
I have more than a dozen pre-1900 IWC pocket watches, of which 12 -representing about 1500 years- are shown above. Most are in close-to-new condition and almost all have signed dials. To give you some idea of rarity, approximate numbers are 21,000 for Jones mostly in the 1870s, and about 20,000 Seelands from 1875-8 (in the mid-1880s there were 300 Bostons produced). There were possibly about 20,000 Pfisters from 1879 through 1884 (my calibre 28 is a low number and probably 1879). If I’ve counted correctly there were about 920 Elgin I’s from 1879-1887.
You also can see the evolution of movement design and construction in the thrid photo: from Jones (top left) to Seeland (top right) to Calibre 28 a bascule Pilier (bottom left) to Elgin. Also note the engraved balance cocks --I may have some close-ups of the decoration later.
Although I'm focusing on pre-1900’s IWCs, I also have many later examples. I’ll tell about those subsequently.
Regards,
Michael

Calibre 28 a bascule Pilier, dial view

Calibre 28 a bascule Pilier, movement view

4 movements: 1874-1886, showing the evolution of early IWC movement construction

12 Pre-1900 IWC watches and 1500 years of history. 3 Jones (lower left) to IWC Calibre (top row)