The RAF strap is not precisely defined, but is commonly referenced as a a long single piece strap, often of nylon, that usually uses a fabric keeper.
The A.F.0210. strap was an Army one piece strap, with brass keepers, developed at the end of WW2 in 1945. British military watches developed after WW2 were for aircraft navigation purposes, and the straps subsequently used were thought of as RAF straps.
Below are some A.F.0210.® homages to the so called RAF strap, a pull through strap with a fabric keeper. ⠀
James Bond wore a RAF strap in the movie Goldfinger, which was released in 1964 before NATO straps became a military specification under the 1973 Ministry of Defence Standard (DefStan) 66-15 for a ‘Strap, Wrist Watch’.⠀
Despite having a reputation for being immaculately dressed, James Bond wore this watch on a 16mm nylon RAF type strap, which does not fit properly between the 20mm lugs on the Rolex Submariner, ref 6538.
The 9 stripe colour scheme is dark oxford blue, peony red and gosling green, the then colour scheme of the Royal Scots Regiment.
The original fabric keeper was sewn in place.
Photo Credit : Watchuseek forum member : Paul Ramon
Post war RAF straps were steel (Bonklip 6B/2763 (17.5 mm), 6B/3224 (19.0mm) and 6B/3033(20.0mm)), canvas webbing (A.F.0210. and 6B/2594), nylon NATO (6B/2617, and NSN 6645-99-124-2986), and the nylon/leather Bund type (NSN 6645-99-527-7059).
Hence the currently numberless pull through strap with fabric keeper is obviously “the” RAF strap.