The 13/1 was (presumably) the first model made by Cyldon and is atypical in some details.
The firebox is a different style from the usual Cyldon type and is steel instead of aluminium.
The meths burner is also slightly different.
The base is made of wood (as is the 13/2 but none of the other models).

The brass boiler is fired by a brass cylindrical three wick meths burner.
It has a safety valve and a separate filler plug and overflow plug and is fitted with a whistle.
It has a dummy chimney.
The boiler is held onto the steel firebox with a single brass band.
The copper steam pipe exits from the bottom of the boiler inside the firebox, thus getting a very small degree of superheat.

The steam is fed directly to the back of the port face of the oscillating cylinder.
The brass cylinder is a single acting oscillating type.
The crank shaft is steel, with a brass disk crank at one end, a small pulley at the other and mazak flywheel in the centre.

This model is vaguely similar in some respects to a one-off model identified as made by Mersey Model Co. Ltd. It has been suggested by some people that the Mersey model was used as a prototype for the Cyldon 13/1 and that there may be a link between the two companies.
 This is very unlikely and there is no known documentation to support this speculation.

A later version of the 13/1 had changes to the firebox and burner which were then adopted in the later models 13/2 - 13/4.
The 13/1 was (presumably) the first model made by Cyldon and is atypical in some details. The firebox is a different style from the usual Cyldon type and is steel instead of aluminium. The meths burner is also slightly different. The base is made of wood (as is the 13/2 but none of the other models).
The brass boiler is fired by a brass cylindrical three wick meths burner. It has a safety valve and a separate filler plug and overflow plug and is fitted with a whistle. It has a dummy chimney. The boiler is held onto the steel firebox with a single brass band. The copper steam pipe exits from the bottom of the boiler inside the firebox, thus getting a very small degree of superheat.
The steam is fed directly to the back of the port face of the oscillating cylinder. The brass cylinder is a single acting oscillating type. The crank shaft is steel, with a brass disk crank at one end, a small pulley at the other and mazak flywheel in the centre.
This model is vaguely similar in some respects to a one-off model identified as made by Mersey Model Co. Ltd. It has been suggested by some people that the Mersey model was used as a prototype for the Cyldon 13/1 and that there may be a link between the two companies.  This is very unlikely and there is no known documentation to support this speculation. 
A later version of the 13/1 had changes to the firebox and burner which were then adopted in the later models 13/2 - 13/4.
Cyldon