Got this through a buy it now on the bay for silly money and has gone straight to the top of my limited military collection.
Hallmarked for Glasgow import and the letter V for 1918/19, .925 for silver and JW (james weir) for the sponsor.
The size is pretty impressive at 35mm without the crown and 38mm with the crown.
The case is stamped with brevet 71363, which believe is the same case rolex used for simlar trench watches
And the movement is where I fall down. I just can't seem to find any info. The only markings are the serial No and swiss made.