Individual locomotives had dimensional variations [1]: 142
The Great Southern and Western Railway (GS&WR) Class 21[Note 1] (Or perhaps more simply engine numbers 21 to 40) consisted of half of the initial order of 40 passenger locomotives ordered for the GS&WR and which entered service between approximately 1845 and 1847. A number were later rebuilt to 2-4-0 locomotives for goods work.[1]: 142
Engine No. 36, built in 1847, covered 300,000 miles (480,000 km) and is preserved at Cork Kent.[1]: 142 There were suggestions it was able to achieve 60 miles per hour (95 km/h) downhill on Ballybrophy bank but climbing out of Kingsbridge towards Inchicore on a wet day might require the fireman to walk alongside shovelling sand under the wheels to prevent slipping.[2]: 192