MST 13 

Remarks: Meyer and Studeli SA (MST) had been in business since 1888, mostly producing cylinder movements. This is the first known ROAMER wrist watch calibre, featuring a jewelled Swiss lever, screwed balance, and separated train bridge design. The earliest UK hallmarked and verifiable watches with this calibre in my collection are from 1916, I also have other UK hallmarked examples from 1917 and 1918, aligning with the WWI period.
This calibre is not listed in any of the known Roamer catalogues - however catalogues prior to Number 3 have not yet been found, and catalogue 3 was when Roamer/MST renumbered their calibres. Documentation, however does exist in 3rd party listings, such as the DCN catalogues from the staff and stem maker, in which this is simply described at the 13 Ligne MST calibre, which I have adopted here. Warning, later MST catalogues use number 13 for a 16L calibre.
In terms of design family - most major features: train pivots; balance cock; barrel, crown, ratchet centers; dial feet; and lever, line up precisely with the later MST175, however the setting works, including the stem are unique and the staff is likewise different. Other differences include the sinuous bridge design, many of the plate screws, and motion works (due to the ancient style centre pin clutch rather than a cannon pinion clutch). One final comment on the setting works, the design is similar to that in the smaller, later calibres: the 202; 251; and 253, it also bears a resemblance to the 18 Ligne 154 and the 19 Ligne 195.
Examples of this calibre exist with 13 or 15 jewels. The number of jewels does not correlate with date - but there are some interesting differences in the calibre that do permit the movement to be roughly dated. All examples seen of this calibre are finished with gilt plates. In 1916 versions the crown wheel is 2 piece, retained by a large top hat inner core, while by 1918 the crownwheel is one piece and rotates around a small steel bearing. 1917 sees both types. A second means of dating is for the 13 jewel versions only. In 1916 the 13 jewel versions the train pivots are fully jeweled, except the lever pivots which are plain. By 1917, the 2 unjeweled pivots were the 3rd and 4th dial side pivots, while the lever was jeweled, which was a much more conventional arrangement.
Production period: 1916-18

Jewels: 13 or 15
Beat: 18000
Winding: manual
Manufacturer: MST
Hand sizes:
Minute: -
Second: -
Stem tap size: 1.3mm A = 100, B = 135, C = 165, F = 517

MST 13 13''' (28.9mm) sub second, first wrist calibre from MST

Common parts/Interchange
Balance Staff:
MST part number:-,  interchanges with MST: -
MST part number:GR4575 interchanges with MST: 175
Strength: 0.135
Height: 1.60
Length: 300
Watches in my collection with the MST13:

All text and images are either © Kris Bubendorfer 2011-23 or © Roamer Watch Company.