NBR 224 and 420 Classes
Summary

Original number
Class
Built
Rebuilt
Renumbered (year)
Withdrawn
224
224
1871
1885, 1887, 1897
1192 (1913)
1919
264
224
1871
1893
1198 (1913)
1917
420
420
1873
1887
1241 (1914)
1915
421
420
1873
1887
1242 (1914)
1918
422
420
1873
1890
1243 (1914)
1918
423
420
1873
1890
1244 (1914)
1914

Question: What years were the 420/421 and 422/423 locomotives rebuilt?
Answer: In the NBR 224 and 420 Classes, the nos. 420/421 were rebuilt in 1887 and nos. 422/423 in 1890.