Marquess of Lansdowne
The title has been held by the head of the Petty-Fitzmaurice family since 1784. In 1956 the eighth Marquess (George John Charles Mercer-Nairne Petty-Fitzmaurice 1912- 1999) and the Marchioness of Lansdowne were among visiting dignitaries from the United Kingdom branch of the Commonwealth Parliamentary Association; visiting Australia for the Centenary of responsible governments in New South Wales, Victoria, Tasmania and South Australia. They arrived in Sydney on the 11th November, afterwards visiting Canberra, Melbourne, Adelaide and Hobart in turn. It is likely the Marquess ordered some buttons from local maker Stokes whilst he was here, or else Stokes had produced them as a gift.
NB: There is no evidence of any previous Marquess of Lansdowne visiting Australia. It would have been expensive and slow for the British to order livery buttons from Australia when they could be ordered locally, that is why I have dated this button as I have.