4158 in mid-1950s condition.  Click pictures to view at full size

The engines which form the basis of this kit were an updated version of the Churchward 2-6-2T engines introduced in 1903. They were divided into two classes the 5101 class (5101-5110, 5150-99, 4100-79) introduced in 1929, for general use, with 200 lb. pressure boilers followed in 1931 by the 61xx class (6100-69), specifically to work accelerated London suburban services, with 225 lb. pressure boilers.

Variations/Modifications incorporated into the kit

Water Fillers: 5101-10, 5150-89, 6100-6109 were fitted with a screw down lid whereas the remaining engines were fitted with a lever type.

Cab shutters: 5190-99, 6110-69 & 4100-79 were so fitted when new. The earlier engines received shutters from 1933 onwards.

ATC equipment: fitted when new to 5160-99, 6130-69 & 4100-79 and applied to the earlier engines between 1930 and 1933.

Journal lubricators mounted on the tank top: The majority of the 51xx & 61xx series were so fitted when built. The 41xx series did not have these lubricators and some of the earlier engines had them subsequently removed.
Step on tank front: 5101-10, 5150-89, 6100-6109 were fitted with a step of traditional appearance. The later engines had a step of the same design as fitted to the rear of the bunker.

Upper front lamp bracket: moved to smokebox door on a few engines.

Spare lamp brackets: on early engines these were mounted towards the footplate edge alongside the splasher; later they were placed further forward and in front of the splasher.

Whistle shields: fitted to 4160-79 when new and later to a few of the earlier engines.

Handrails on tank strap: two extra handrails were added on the strap over the boiler from circa 1945 onwards.

Bunker steps: Welding of three steps to the left side of the bunker began in 1952. This necessitated the shortening the handrail on the bunker side whilst at the same time two extra handrails were added one to the rear of the cab cut-out and one on the cab roof.

Variations/Modifications not incorporated into the kit

Safety valve bonnets: 5101-5110 & 5150-59 were fitted with tall safety valve bonnets. The safety valve bonnet supplied is the short type fitted to the remaining engines.

Bunkers: 5101-5110 came out with a recessed fender above the bunker top only, whilst Nos. 5150 onwards had the upper half of the bunker extension recessed to match, as per the kit. Several of the earlier engines have subsequently been similarly treated.

Trip gear: The 61xx series worked over the electrified lines in the London area and all were fitted with trip gear for automatic brake application in case of over-running an adverse signal. The A.T.C. apparatus on these engines was arranged to clip up automatically on entering an electrified section.