This is a nice example of the later 00 gauge Triang piston block assembly all as per the photo and title. It may fit others ??.
Hornby Triang R53 Princess Elizabeth Class 46201 OO Gauge. Runner Ref OL25
HORNBY TRIANG X261 CYLINDER BLOCK FOR BATTLE OF BRITAIN CLASS LOCO REPRO
HORNBY TRIANG X261 CYLINDER BLOCK FOR BATTLE OF BRITAIN CLASS LOCO NEW