Wow Mary, I really appreciate your help!
Re: "How do you know that she died in 1973?"
I have visited the grave she shares with John Douglas in Yarrawonga. Her date of death is 17 Aug 1973. I was also able to obtain a record of her death from the BMD online.
Shirley's family has been much easier to corroborate so I don't really require too much information on her or the Gilbert's. It's really only a marriage record or personal information from someone about her marriage that I require.
Re: "Is this article, dated, 26 Feb 1953, your John KOHN?"
I believe this John Kohne is different as I have found multiple advertising pages for a salon in Benalla with this name mentioned;
http://trove.nla.gov.au/ndp/del/article/65504665?searchTerm=... kohne"&searchLimits=l-state=Victoria|||l-title=216
Given the electoral rolls state John Douglas was a labourer and grader operator, I don't think this fits. I do however think that this link below could be him as a junior farmer, named Jack Kohn. I've found a number of articles of similar topic. It fits with his age and the local area and family the public family trees had mentioned here on Ancestry but it doesn't connect any further dots than that.
http://trove.nla.gov.au/ndp/del/article/117510551?searchTerm... kohn"&searchLimits=l-state=New+South+Wales|||l-title=451
kb