That depends entirely by class of vehicle....
Alliance Knuckles fitted when new,
1932 Wellington EMU's
late 1930's 56 footer Carriages
early 1940's to rebuilt older 50ft'er Carriages when converted to steel collision ends,
1955 built 88seater Railcars
1969 U
K ISO container flats (maybe
ld memory of a 1970's conversation), reconverted to freight coupler of larger proportions than steam era drawgear.
1971 GE D
X locomotives reconverted to freight coupler of larger proportions than steam era drawgear.
1971 Coal bogie hoppers (run as Unit train)
1971 Silver Star Carriages(most likely Tightlocks)
<1981 USL log bogie flats (run as Unit train)
mid-80's USG LPG bogie gas wagons (enormous shelf couplers)
wholesale changeover of the fleet around 2012> once the new blocking of trainsets for freight happened and even then some older classes not changed just permanently coupled with Kidneylinks or Transtionheads until withdrawn from service or rebuilt. Several variations in size of the replacement couplerhead.
As for steam, considered Heritage Vehicles I doubt it, that would require some serious investment in structural modification and resultant certification.
Edited 2 time(s). Last edit at 10/04/2019 06:16PM by Chris Walker.