WW1 Pin ID?

[Geoff Winnington-Ball (RIP)]

Gentlemen,

Received through email the following pic along with an enquiry as to just what this is. Note the crossed Ross Rifles, the Maple Leaf with Cross of St. George emblazoned thereon, and the 'CASF' identity.

Has anyone seen this before, and if so, can you provide what information you can? The lady who sent this in would very much like to know. WW1 or before? Post WW1? Significance?

Thanks,

Jif