The Mk3a carriages were constructed by BREL Derby Litchurch Lane Works between 1975 and 1984. The Mk3a carriages are basically the locomotive hauled version of the Mk3 coaching stock used on InterCity 125 high speed trainsets, except that they have buffers and dropdown buckeye couplings fitted so that they can be hauled by conventional locomotives.

Initially Second Open (SO) and First Open (FO) variants were constructed, followed by Restaurant First Buffet (RFB) vehicles in 1979-80.

This coach has been repainted in full Caledonian Sleeper livery as carried on CAF Mk5 carriages that were introduced in 2019.

This reskin requires the WCML North Add-On from Steam, available from: https://store.steampowered.com/app/24083