Good research there, Jack.
AFAIK, Bragg Industries originated the Jetfast brand, and may have later changed their company name to include 'Jetfast'.
The ASIC website is down today, so I can't run any business name history searches.
It can be informative to run a few trademark searches at
http://www.ipaustralia.com.auBragg Industries, Jetfast Supaswift and Allpower all had relevant mower-related trademarks registered at one time or another.
'Assignment' in the records means that the TM was transferred to a different company, AFAIK.
The company name succession appears to be Bragg Industries P/L [to late 1970's], then Jetfast Industries P/L [early 1980's], then Jetfast Supaswift P/L [late 1980's], quickly followed by Allpower Industries P/L.
Jetfast Industries Pty Ltd were definitely trading in the mid-1980's - my 1985ish SupaSwift Big Bob has that name on it as manufacturer.