Riddell may have seen service in Siberia in the "B" Squadron ("B" Squadron, Royal North West Mounted Police, Siberia 1918/12/01-1919/05/26) but his name does not appear in on-line resources related to this service.
On his Officers' Declaration the medical officer found him unfit for service due to his being 59 years old. Despite this, he was not demobilized until Sep 15, 1919 as part of the general demobilization.
The Canadian Almanac (1916) lists his war service awards as:
- Rebellion in the Northwest Territories in 1885 - medal and clasp (probably for Cut Knife Hill, 2 May)
- South Africa (2nd Boer War) 1900-1902 - Queen's medal and 4 clasps