There was reference in the correspondence unearthed by Clive Law to additional Ross bases being made up in Canadabefore WWII so as to make up the shortfall of rifles as compared to scopes then in store.
The shortfall in rifles was presumably due to their having been scrapped as unserviceable following WWI service, whether in training use or otherwise. That or they were "lost" somewhere in the ordnance stores due to improper record keeping. Clive Law pointed out that the rifles and scopes were in the 1930s actually stored in separate depots, one in Quebec and one in Ontario!
The bases used on the Patt.14 rifles were probably new-made Ross bases modified to suit at some point.