A nice detail I spotted for the first time is the screw coupling has a very short top link and is secured to a shackle in the coupling hook. All 9Fs seem to be like this.

Robert Waterman says "This was the standard coupling fitted to the 9Fs as built, which was the Southern Railway/Region standard Ashford SECR pattern type. See any SR loco such as the Bulleids, Lord Nelsons, Schools, U and N class etc. Right at the end some 9Fs were retro fitted with heavy diesel type couplings. All the other 'standards' were fitted with LNER pattern couplings so far as I know".