Many thanks Eezy. With your excellent photos and info I can now be fairly certain that the strap attached to the fixed lugs of my 1945 www Vertex is the original “army issue “ pigskin strap that was issued with the watch. I found a good article at “The history of the nato watch strap part 2. The nato watch strap during world war 2.” which I came across on AF0210strap.com website. This shows a www Record watch with the same “army issue” pigskin strap.
I am trying to find images of the pigskin watch straps that were attached to the dirty dozen www 1945 military watches when issued to U.K. military personnel.