Two very early ones. This is GWR No 7 from 1859, Wolverhampton works no 1, and the first Joseph Armstrong design for the GWR. Holcroft tells us that Armstrong, very much a member of the Northumberland school, was much associated with George Gray. Gray's designs for the Hull & Selby and LBSCR had the same feature of inside frames on the driving wheels and outside on leading and trailing wheels. They were also the inspiration for the well known Jenny Lind type. My sources are quiet on what motion was fitted. There were eventually five of these early singles. No 8 was very much a sister of No 7 and came out the same year, whilst 30 and 32 (the last classed as a renewal) followed in 1860 and finally No 110 in 1862. They didn't really constitute a class, but had a number of common features.  There are plate frames rather than the sandwich frames Gooch would have used, and the very complex shaped Armstrong safety valve cover.  Early Armstrong boilers like this were domeless, although domes were adopted fairly soon.

The last of these similar singles was GWR No 110 from 1862. Surprisingly it was the second No 110, the first having been an 1851 locomotive for the Birkenhead Railway which lasted hardly a year under Armstrong. It's worth noting that by this time Armstrong had about 70 locomotives in his charge of many designs from most of the significant manufacturers of the period, so he should have been in a strong position to evaluate the best features for his own design. Unlike its predecessors No 110 had outside bearings on the driving wheels.  This 110 bears a distinct family resemblance to the 111 class 2-4-0s which came along in 1863. 

In later years the 1862 110 received larger cylinders, a weatherboard and maybe even a cab. It ran until 1887, when it was renewed as a 2-4-0 of the 111 class in the form that class had been rebuilt into at that time. It seems unlikely that many if any major components were reused. By contrast No 7 had been withdrawn in 1876, some years before any of its cousins, and seems to have been largely unaltered.