It has always been thought that there were only two versions on the side of the locker box but Nick Jones discovered a new version a while back and this may well have been a a trial or a very first issue. My own opinion is that it was as intended but modified with the two raised bars to help in decal placement on the production line. I include Nick's photos of this very rare version here so you can see the difference and it is interesting to note that the horses are as the 'grey' version (pics.8, 9 and 10).

The next version had London labels and these can have a gold border or black one. Some have been described as navy blue border but I have never been able to see the difference between navy and black borders. These models can have the label placed over the first issue boiler sides so the two raised bars can be seen underneath and are a rare version (pic.4). The horses had now become black with white manes and once again as time went on they became all over black. A rare short run had the horses in a metallic bronzy finish and these are scarce. Modifications were made to the drawbar, being fixed by one rivet and later 2 on a square plate. The rear step behind the boiler also had several interesting modifications to it starting with 9 full slots and 3 half slots, then 7 full slots only  and finally with the support arms thickened up for extra strength in this fragile area (pics. 11, 12 & 13).