Interesting to finally see a firmer account of the Maxim silencers, given the "whispering death" references found here and there in the literature - which ostensibly referred to their use in France.
Am not aware of any primary source reference to their use in France however, but if they were in use at Gallipoli in 1915, there would have been no reason not to also used them in France, particularly after with withdrawal and the good reports(?) of their use there.
Presumably the "bayonet mount" type rather than the interrupted thread as modifying rifles was a minor heresy at the time.
(There would been nowhere to attach to an SMLE obviously)
I wonder if any Maxim sales records exist; though such purchases might well have been "off the books", if only to keep Maxim's German-American workers from sabotage etc.