Because I was wondering something along the same lines the other day.
The 6B/159 watch is pretty well known and shows up from time to time on Ebay. I have two of these watches. According to Mick Prodger's book, this watch became obsolete early in the war and a different watch, one with more functions (chrono?) became available. Does anyone know what this watch looks like?
There's some pretty nice pictures of RAF wartime watches on this site: http://www.tommyvintage.com/ommil.html
But if the later pilot watch is pictured there, I don't know which one it is.
Anyone have further info?