I hope this is appropriately posted here. If not, my apologies, but for those Hand Ejector .455 owners with names or initials affixed to the firearms or accoutrements and wondering if they might indicate Canadian usage in the Great War, there's a small window of opportunity for you to maybe fill in some blanks.
To honour the anniversary of the Vimy Ridge battle in the Great War, April 9, Ancestry.ca has opened up free/trial access to its database of First War Attestation papers for the next couple of days. Not a full history by any means, but these records often point to initial battalion postings.
Good luck.