Noel, very interested in the TPO project , I think they had the mail catching gear until the late sixties here's another gem from the O'Dea collection from 1967 which show's the TPO forth coach from the loco with the apparatus still attached also interesting is the coach behind the loco some old GSWR coach with whats looks like the windows painted /covered over and possibly being used as van?.
http://catalogue.nli.ie/Record/vtls000306219