Hello swampyro
As the Forum Historian, I only have interest in the early Rovers,
up to about 1980.
At this time the model range was easy.
However, Model lists were problematic - in that Rover always
linked model number to engine used.
A search on the Blue Bar (above) for 'Rover Brochure' should
identify the Model numbers for ride-ons up to about 1980.
After that, who knows?
After the '80's the corporate 'rag-doll' of change-of-ownership makes
tracing a time line, and model ID difficult.
That's the modern world of garden machinery we have inherited.
Sorry I couldn't help.
I hope a Rover enthusiast may have done some research here...?
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Jack