The class 57 are rebuilds of class 47 locomotives and so appear outwardly very similar. The rebuilds took place from 1998-2004 and included different engines and traction alternators to the originals.
https://en.wikipedia.org/wiki/British_Rail_Class_57
Current operators include DRS, GWR & ROG, plus WCRC has a fleet of class 57s primarily for railtour work.
Tony