Shortly after publication, I found an album with two of his postcards addressed to "Master Elmer French", his baby brother at the time. Elmer became my father. 

I'll present them here. They came from overseas.

In the first postcard, printed text on the back said:

The Pet of the Regiment

An extraordinary assortment of mascots and pets accompanies the Canadian Contingent. Dogs and goats and other animals are numerous. One regiment actually adopted a small boy, a newspaper seller, who was anxious to go with them. He was smuggled somehow on to a transport, and has since become a bugler.

In the second postcard, Oscar's letter to Elmer was short and simple: Well Elmer I suppose Santa Claus will be around when you get this. He has to go around in a waggon here as there is no snow on the ground. From Oscar. It was written in December 1915.