Do you think that Webley could have had a number of "odds and ends" of steel bodies from several years, and used them up just prior to introducing the MK 2 aluminium-bodied model? I seem to have read that the only difference between the blued "E" and "F" was the new 12-groove rifled barrel, as fitted to the MK 2. This could explain why a lot of "F" model pistols have dates before some "E" models.