This is Andrew Mack, the Irish American comedian/singer, who toured Australia in 1905. He liked it so much he returned in 1907.
The inscription says, "A Tribute in memory of your debut from The Knuts. 1917." The back of the card looks like this.
The handwriting says," From your stage assistant." The print identifies the card as being a souvenir from the , " National Committee of YMCAs on active service with the Australian Imperial Forces."
So is it a wartime joke? or a souvenir of a performance? It certainly is interesting.
The postcard fair always provides surprises!