Graham’s comment about couplings sent me scurrying off to the book room to look for more info. Far from finding definitive answers, I’ve found that coupling types in use during the period were legion; three link, four link, five link, three link plus one for shunting, links (of different numbers) with a hook (sometimes short, sometimes long) on the end, short links, long links, short pilot screw links, long screw links, side chains (with different numbers of links), and more besides! As for the coupling hook, there were Gedge hooks, plain hooks, some locos had an an eye-bolt and no hook! Solid hooks, swinging hooks, ad nausium. Even more hair-raising was that different members of the same class on identical duties could have different coupling types, and some locos wore two or even three types of coupling at once. Sometimes these multiple types were hung loose over the hook, sometimes they were attached to a common hook (or eyebolt). Mad. Just mad.