Thanks, all, for your continuing efforts. From all the really useful comments it appears that the date is significant and the chimney and dome types are therefore significant. If the loco can be ultimately identified it'll one of the great pieces of detective work!
Larry - I agree that the speed of Panatomic X could be a problem, but, let's face it, the film was never intended for photographing moving trains! It was a great film for portraits, though, and that would include locomotives. At the time many of us were using Kodachrome slide film (25ASA) or Kodacolor negative film (32ASA and later 64ASA). The higher speed Ektachromes were quite useful but the images were known to be less permanent than Kodachrome although mine seem to have survived OK.
Now, continuing the Scottish trip.
First a general view at Connel Ferry on 12th September 1961 with 0-4-4T 55260 approaching in the distance.
Still at Connel Ferry on 12th September 1961 and 55260. This moved to Oban shed in March 1961 and in August 1962 to Perth South from where it was withdrawn at the end of the same year (SLS). It was scrapped at Arnott Young, Carmyle, during October 1963.
More modern motive power here with Ivatt 2MT 2-6-0 46458 at Connel Ferry on 12th September 1961. That certainly looks as though that's the number on the cab side, but could this be another example of mistaken identity as 46458 was a Kirkby Stephen engine until December 1961 when it moved to Carlisle Upperby? It was withdrawn at the end of December 1966. (SLS). It went to Motherwell Machinery & Scrap at Wishaw where it was broken up by the end of May 1967. (Rail UK).
Edit: Actually probably 46468 which was at Oban at the time in question. See further details in posts below.
Here's an interesting one - well, two actually. An NBR 0-4-0 saddle tank from 1890, LNER class Y9 No 68104 at Stewarts & Lloyds Steelworks Yard with "Polmont" on the buffer beam on 13th September 1961. The SLS records this as a Kipps loco from December 1960 but one of the Polmont allocation before that, so I'll guess that the name on the buffer beam was never updated. Somewhat annoyingly the shed plate is obscured. I'll hazard a guess that the loco is on loan to the steelworks. 68104 was one of the last two Y9s working, both from Kipps, the other being 68117. It was finally withdrawn in October 1962. (SLS). It went to Cowlairs Works for disposal which was complete by the end of September 1963. (Rail UK).
Brian