I'm more convinced that the first Model Lawn King dates from the early 1970s. Its factory colour was gold and white and not 'Bonmow Blue'. It was a Model 33 with an updated transmission. These components were factory original and not retrofitted (best guess).
These are fairly rare machines for the reasons I've stated. Here's an auction record from last year. Note the clutch spacer:- [I hope this is not the exact-same mower as kymbom2g's?]
Here's a YouTube video of one:-
[video][/video]
Here's the best ad. I could find. It's not clear but it does seem to corroborate a front clutch lever (maybe):-