Hello wce
It goes unrecognised, that the Mayfair was probably Victa's most successful model - ever!

I have written about the importance of the Mayfair to the Victa story here:

https://www.outdoorking-forum.com.au/forum/u...mayfair-victa-s-first-stencil-c1965.html

I choose to just discuss the mower you have raised in the above images.

Okay, There has been some shenanigans going on with your machine.
The engine (1968) predates this early-to-mid 1970's chassis...

The slotted base (exhaust vent) was to accommodate the box-style muffler of the 1970s Mayfairs.


The experts should be able to explain this better.

Cheers
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Jack