There were actually two 157 classes. The first, above, was specified by Gooch and built by Sharp Stewart in 1862. They could be regarded as a development of the earlier 69 class with larger driving wheels. They were numbered 157-166. They were little altered in their lives, with only one receiving a new boiler, from an Armstrong Goods. They did receive weatherboards and it is possible that some may have been given open cabs.

Most were scrapped in 1878/9 when the new 157 class took over their numbers. The last three stayed in service until 1881; these survivors were renumbered 172-4 for their declining years.

I don't usually put drawings up here that are featured in my book unless very heavily updated, but I thought both 157 classes should be in this piece. Normally 19thC heavy rebuilds, even those reusing "only the space between the wheels" were classified as renewals, but RCTS tells us the second 157s were classified as new. Its interesting that even when renewals were effectively all new locomotives they tended to keep the same frame type as their predecessors as these did. As with most of the later 19thC classes they had a healthy variety of different boilers fitted over their lives, domes and domeless, belpaire or round topped box. This sketch is intended to be representative for around 1900. A little prototypical note though: I typically draw my locomotives bearing the class number, so 157 here. But to be strictly correct then as I read RCTS 157 herself  never actually ran with a domeless Belpaire firebox boiler. 

And finally a Wolverhampton variant of the class, discussed in comments below.