Greetings all,
That Webb does look like a well-built machine, but not common in Oz.
The Old Lawnmower Company also lists the Operators Manual for these;
http://www.oldlawnmowers.co.uk/ol-literature.phpNot for free, of course!
We can say that the engine is pre-1982 [easy-spin start]. We can give the engine's exact production date, and pointers to a parts list, if you could post the Model, Type and Code numbers from the cowling.