The LNER Class Y3 was a class of 0-4-0 geared steam locomotives built by Sentinel Waggon Works for the London and North Eastern Railway and introduced in 1927.
They passed into British Railways ownership in 1948 and were numbered 68154-68185.
[2] The superheated vertical water-tube boiler and the engine were similar to those used in Sentinel steam wagons.
The engines had poppet valves and reversing was by sliding camshaft.
In addition, there was a two-speed gearbox but gears could only be changed while the locomotive was stationary.