The range of 1937 pattern webbing items produced in the RAF’s blue grey was extensive and included all the standard rifleman’s equipment, including the pack and its accompanying supporting straps. The supporting straps had been introduced with the 1908 pattern set, however in blue-grey they were exclusively for use with the 1937 pattern pack:

The straps crossed the back of the pack and allowed the shoulder straps to be attached as well as securing a helmet in place when required. In this view of a full set of RAF marching order they are clearly visible on the pack:

The RAF’s webbing never adopted the blackened fittings of the army’s pattern, so the buckles of these supporting straps are made of brass:

When purchasing a set of RAF supporting straps, take care as the same pattern and a very similar colour were used by the post war Belgian Army as well. British made examples will have a British maker’s initials on them, and if the date is before 1945 you can be confident it is an RAF example. Often the markings are pretty faded, as here, but it is clearer in real life and this example is definitely of British production:

If you want to learn more about 1937 Pattern Webbing, check out my new book on the equipment set that can be found here.