The "Type K", number 801 was a diesel locomotive which was allocated to Córas Iompair Éireann (CIÉ) following the disbanding of the Great Northern Railway Board (GNRB) in 1958.
The locomotive closely followed German practice being fitted with an 800 hp (600 kW) MaK diesel engine, feeding power to the rails through a Voith torque converter.
The locomotive shared many similarities with the less powerful Deutsche Bundesbahn class V65, it had a "D" (8-coupled) wheel arrangement and was controlled from an off-centre cab.
The locomotive underwent trials on both goods and passenger trains over various parts of the GNRB system and on some of the Ulster Transport Authority's former Northern Counties Committee lines.
Trials between Dublin and Kildare and on Dublin–Bray passenger trains followed before K801 was transferred to Cork, where it worked mainly on the Cobh and Youghal lines.