Simon Darvill has identified the “third” steam locomotive in Kabul.
It is Henschel 19691 of 1923. The entry for it (and for 19680-1) is “Ferrostaal for Kabul-Darulaman, Afghanistan, British India”.
Meanwhile, a blogger in Kabul called Liz went to visit the Kabul museum last month, and provides links describing the revival of the museum. There is also a big photo of the plinthed loco in the snow.