Side Cap

Its very true that the side cap or 'Cap, Field service' was an item of clothing first introduced in December 1939, although thats on the assumption this is an RAF worn cap. As I mentioned there were a number of Air Forces, some no longer extant, which it may belong to, whose dress regulations Im not certain of. As many, such as the Ceylon Air Force and Indian Air Force were in hot climes, it might well have been worn prior to WW2, even though English made.

However the details are of interest. One thing that struck me was the fact that although appearing to be an Air Rank cap, the badge clearly isnt. However, when first introduced the new dress regulations stated that the badge was to be, '...An eagle and crown in gilt metal for officers of all ranks, showing the eagle flying from front to rear...'. There is no mention of a special badge for officers of Air Rank, even though such a badge was worn full sized on the service dress/peaked cap. So if it is RAF its quite possible it is indeed a very early Air Rank cap. I can't find anything on the colour of the piping, but its a possibility that the initial caps for officers of Air Rank had gold piping (possibly only as a trial), replaced within a very short time by the more familiar Air Rank cap we know now. Certainly, of the photos I have of Dowding wearing a side cap during the Battle of Britain he seems to be wearing the miniature version of the Air Rank Badge (as does the King during the same period), meaning the cap for Air Rank officers with standard badge (as Paul has) seemingly lasted only 6 months at most. If an Air Rank officer had Pauls cap, and new regulations came in stating that the cap to be worn by officers of Air Commodore or above was to have a new badge (the miniature AO badge) and blue not gold piping, it would mean more than just a badge replacement, but a whole new cap.

The buttons are interesting. Paul did say initially they were both Kings Crown. Regulations specify that they were 'No. 5' for the Side Cap (No. 1 was for Service Dress jackets and Greatcoats at 9/10ths inch in size; No. 2 was for Service Dress jacket pockets, as well as the shoulders of the khaki Service Dress at 7/10ths inch; and No. 3, which was for Greatcoats at 6/10ths inch. All are described as 'gilding metal, die struck, fire gilt'. No mention is made of a No. 4). The No. 5 button is described as 11/20ths inch, 'Gilding metal shell, eagle and crown of fire gilt'.

Note there is no mention of wearing the No.5 button on Mess Dress, only the Side Cap. The Mess Dress had by this time been abolished, although the buttons would almost certainly have been the same as those specified for the side cap in December 1939. Earlier dress regulations mention size rather than a number.