1st Infantry Volunteer Regiment
Thanks to Jamey Blewitt for allowing me to use these images of a West Australian Volunteer Officer’s mess dress jacket and vest. It is for sale on Ebay. There are four buttons on both the vest and jacket, with another two on each sleeve cuff.
In J. K. Cossum’s book “Buttons of the Defence Forces in Australia” the button with the Swan upon it is named as belonging to the Perth Rifle Volunteers, 1893-1901. It is better named as from the 1st Infantry Volunteer Regiment, formed from the Perth, Guilford and Fremantle Rifle Volunteer corps in 1893.
The West Australian (Perth), 17th November 1893, page 6.

Backmark: Herbert & Co. London. I missed out on this one!
There are also examples by Samuel Bros. Ltd. London.