Info on Ransomes Fourteen/Sixteen Mowers

I am still trying to track down information in respect of the above machine models.

The Sixteen that I have looks to be about 1960 but this is a guess. I suspect it came before the Mercury 16.

The one I have is fitted with the Norton Villiers DO7 engine but again I haven't been able to track down when these were made.

I would be grateful for any info relating to the dates when these machines were manufactured or any ideas of knowledgable sources where research might reveal this.