Not sure if a workshop manual was produced. The owners handbook includes a parts list for the machine. There is a separate manual for the Villiers engine.
If it has the original JAP engine then it should be possible to get the year from the engine number. JAP used a letter to indicate year. See JAP engine numbering
Merry Christmas to everyone. Thank you to all club members that have renewed and special thanks to those that have included cards, good wishes and thank you messages, it is appreciated.
Not sure this forum is the right place for this question, we tend to specialise in old garden machinery not plants.
I would suggest contacting the Royal Botanical Gardens at Kew.