I don't think this will answer your questions, but I thought I would add this for anyone interested in the history of this machine. In the early 1970's I worked for a company, Garden Mechanisation in High Wycombe. This was the lawnmower sales and service company owned by Gerry Hazlewood, who subsequently went on to form Westwood Engineering. At some point, Westwood had purchased a stock of Dynamark Tractors from the US (I think). These had been shipped to High Wycombe in bulk and stored at the rear of the Garden Mech location on the A40 east of High Wycombe. Problems were; these were not initially sold in any quantity and also their storage location was at the bottom of the yard alongside the River Wye (the Buckinghamshire, not Herefordshire Wye). The river Wye routinely floods in winter, meaning these units were frequently waterlogged for extended periods. As a somewhat junior engineer, I was often tasked with unpacking one of these from their soggy cardboard boxes and trying to get them to function again as tractors. On most occasions I managed it, and these went on to be sold to some unsuspecting customer. Please accept my belated apologies for the condition of your mower, if it was one of mine.