It is a challenge to find dated Roamer Trench watches, below is a timeline of the watches in my collection, starting with a 1917 Black Dial MST157 in a hallmarked silver case on the left, and on the right the last MST 175 models from the late 1920s. The dates given indicate the UK hallmarked cases which can be dated exactly, the remaining watches are placed in a continuum between these in approximate (read guessed) date order, based on dial, font, movement finish etc.
The top two watches in the 1918 column are calibre MST157, the bottom two MST175 – after this all production was MST175. 8 Watches are Sterling Silver, 6 of which are UK hallmarked, one is Gold filled, and the remaining 3 are in Nickel cases.
While I have seen one or two ‘Roamer’ trench watches dated earlier than my 1917 example (one was 1913) I believe these are recessed – for various reasons including case screw marks and the essential point that the merger with Tieche-Gammeter appears to coincide with the use of the Roamer name and the use of lever watch movements. This is not true for Medana incidentally. For these reasons, unless we uncover some new and compelling evidence, I would look suspiciously at any Roamer trench watch dated to before 1917.