An item referred to The Marine Engineer dated July 1920 dealing with the small British monitors M 15-33 built during the First World War in 3 types.
The M 15-18, with a displacement of 570 ton, speed 12 knots, draught 2,3 metres and 1-23cm L/50 gun.
The M 19-28, with a displacement of 570 ton, speed 9-10 knots, draught 2,3 metres and 1-23cm L/40 gun.
The M 29-33, with a displacement of 580 ton, speed 10 knots, draught 1,8 metres and 2-23cm L/50 guns.
Each monitor was built within 4 months. The M 18-20 and 23-28 fitted out with engines. Some monitors were lost, the M 22 and 31 were to be converted into minelayers, the others were to be broken up.
