Hi Willo
These are great images for the record.
The Model Type & Code on the engine will give an accurate date of production.

The closest brochure info may be found here: -
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/60888/webb-range-1970s.html

This is a 14" Web Standard form the 1970s ... best guess.

Many thanks for recording your machine.
These were well-designed and built British reel mowers.

Cheers
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Jack