And if anyone's interested, that scene, with the railway engines too in the shed, is filmed at Didcot Railway Centre in the Uk which has a WW1 1917 built steam locomotive which served in France and is in WW1 khaki Railway Operating Division colours
what surprised me the most was the kind of "sten gun" used by the heroes in this sequence. there was no clear view of it but i could not identify it ...
Looked to me like it was based on a Madsen - especially with the vertical curved magazine
http://en.m.wikipedia.org/w/index.php?title=Madsen_machine_gun&mobileaction=view_normal_site
Picture enclosed. Suggestions include Villar-Perosa OVP M1918 or Beretta M1918, but they're pretty wide of the mark. There is, though, more than a hint of the M1895 .303 Maxim. I suspect the likeliest explanation is that it was dreamed up by the Props Dept., perhaps with a little advice from a Steampunk consultant.
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