Anyone following this will gather that I'm currently working on very early Wolverhampton classes.
The 111 Class was the first real class to be designed and built by Joseph Armstrong at Wolverhampton, but to my mind its very much a development of the earlier singles I've previously sketched here. 
 

The first six were built in 1863/4 under Joseph Armstrong. They had outside plate frames with the footplate rising in curves to clear the coupling rods, 6ft0in driving wheels and 16x24in cylinders. This first batch had raised round top fireboxes and no domes.

Twelve more followed in 1866/7 after Joseph had been promoted to Swindon. These could be considered to be George Armstrong designs and were built with domed boilers. Initially they all had open splashers and weatherboards.

In the eccentric numbering of the GWR early days, the first batch of six in 1863/4 was numbered 111-114, 115A and 116A.

Eleven more followed in 1866. The first four were numbered 5A, 6A, 7A, 8A and renumbered 1006-1009 soon afterwards. That same year 115A and 116A were renumbered 1004/5. 372-7 and 1010/11 followed, the last being completed in January 1867.

Cabs and enclosed splashers appeared by the late 1880s, along with larger cylinders and thicker tyres, bringing the wheels up to 6ft 2in.  In 1866 Nos 30 and 110, two of the early Wolverhampton singles, were renewed into locomotives of this class with all these features.

A considerable variety of boilers were fitted in their later years, encompassing not only varying dome positions, but also boilers as small as the Metro and as large as the Standard Goods.

Most were withdrawn between 1903 and 1906, but a few lingered on longer, the last being scrapped in 1914.