‘Tractor build’ isn’t a great advert for aircraft, but the other way? A CAC Wirraway presented anonymously on a brochure for tractor spark plugs. ‘Aircraft Quality’ may be the advert, but certified for aircraft use usually meant prices exponentially greater than for land transport.

It’s a ‘Publicity Brochure – H.V. McKay Massey Harris, Spark Plugs, 1948’

And the Museum Victoria website adds:

Produced in 1948, this small but information-rich pamphlet emphasises the post-war benefits of the technical advances introduced during World War II. The cover graphically links a post-war tractor with the locally built Wirraway trainer, both examples of locally designed and built successful technology. The technological aspects of the spark plugs are detailed, as is the pricing structure.