MST 427 

Remarks: The 427 was a replacement for the earlier MST 417 Alarm claibre, with some internal refinements to the alarm mechanism. The calibres are almost identical externally, the only visible difference being a small hole in the alarm barrel bridge in the 417, near the hammer piviot. Most parts are interchangeable between the 417 and 427, the major difference is in the alarm cancel mechanism, with changes to the levers, springs and hammer. The 417/427 were a completely original alarm calibre design, featuring 2 barrels - main and alarm, both wound from the same crown. Similar in design to the Vulcain Cricket in that it uses a crown wheel rocker to switch between barrels depending on direction crown is wound. Roamer took out patents relating to the design of the special sounding back.
Production period: 1955-1960 (est)

Jewels: 17
Beat: 18000
Winding: manual
Manufacturer: MST
Hand sizes:
Minute: 90
Second: 19
4th hand: 220
Stem tap size: N/A

MST 427 12''' (27mm) Alarm

Common parts/Interchange
Balance Staff:
MST part number:7480,  interchanges with MST: 427
Multiple mainsprings possible:
MST part number:1270 (Main) interchanges with MST: 427
Strength: 0.1100
Height: 130
Length: 345
MST part number:1282 (Alarm) interchanges with MST: Nil
Strength: 0.825
Height: 180
Length: 320
Associated Patents:
CH321585Improved alarm hammer mechanism
Deposited 1955, granted 1957
Watches in my collection with the MST427:

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