For the branch line between Gortatlea and Castleisland in Kerry County, the Castleisland Railway had No. 90 built in the GS&WR'S workshop at Inchicore in 1875. This special 0-6-4 well tank locomotive can be described as a precursor to the steam railcar. Since commercial traffic with regular passenger trains could hardly be carried out on the line, an extra light tank locomotive was combined with a passenger compartment. Some years later, the GS&WR built two more locomotives of this type which were numbered 91 and 92. However, according to Locomotive Magazine, issue May 1903, the passenger compartments were not actually used for their intended purpose.

So in 1890, numbers 99 and 100 were built with a similar boiler and running gear, but as 0-6-0 side tank locomotives without a passenger compartment. These were used on the Fermoy-Mitchelstown line in Cork County, which used a very light rail profile, only 50 pounds per yard. While no heavier locomotives could be used there, the axle load of the two vehicles was low enough. Here they had to conquer gradients of 1 in 60. They spent the last years of their service as shunting locomotives in the port of Cork. The last one in service was 90 that survived until the beginning of the sixties.