A conversion is taking a steam roller and turning it into a different type of machine in which style it is in a permanent state.
A convertible is a combined engine (in Aveling & Porter's terms) which can be either a steam roller or a traction engine/tractor and is able to be swapped between the two in a relatively short time - i.e. less than half a day.
In the light of further in depth investigations in the RLS records, there is circumstantial evidence that Marshall 53351 may have been in traction engine form at one time during its working life. However, this is not definite and cannot be proved.
It is known that Marshall's original records indicate that roller wheels and traction engine wheels were supplied with the order for Marshall 53351 - but equally, it may have been convenient for Bridgwater Council to order traction engine wheels at that time for something else - we do not know for definite.
With these facts in mind, the Association wishes to give its Member who owns Marshall 53351, now in traction engine form, the benefit of the doubt on this particular roller conversion and wishes to apologise for any inconvenience caused. The Association also wishes to stress that it is against conversions in preservation times - for whatever reason - unless they are into the mode of a true convertible (see definition above).
It is recorded in Marshall’s records as being described as a convertible, and was supplied with both sets of wheels – however, to the best of the Association’s knowledge, having taken advice from the RLS whose records are second to none, this machine has never been in any other form than a roller.
In the RRA’s opinion, this engine is a conversion – in preservation days.