G'day folks,
Check the 4-stroke mower pic in the 1960 HG Palmer ad here;
https://trove.nla.gov.au/newspaper/article/103112218?Looks a pretty good match, from specs and what detail is visible.
Very different design to this Briggs engined HGP from 1963;
https://trove.nla.gov.au/newspaper/article/104288940?However, HGP never manufactured mowers; they just ordered their 'house branded' models from a variety of existing manufacturers AFAIK.
If you'd like to look at more HGP ads/articles on Trove, our esteemed Forum Historian has created a useful source list;
https://trove.nla.gov.au/list?id=24369 
